ISOLDE newsletter Spring 2012 http://www.cern.ch/isolde

Introduction measurements of 21-32Mg and 12Be and the 96 COULEX of Kr, which confirmed the The ISOLDE experimental campaign 2011 previous results of ISOLTRAP and COLLAPS was highly successful. Forty-nine pointing to a smooth onset of deformation experiments and as many as 8 test runs in neutron-rich Kr isotopes. You will also were scheduled, which collected data using read about the continued R&D on targets over 90 different beams. The number of and ion sources which is indispensable to shifts delivered increased by 20% over ensure the pre-eminence of ISOLDE as a 2010. As you will read among the highlights world-leading ISOL facility. presented in this newsletter, a first In order to maximise the amount of beam production run on 35Ar for WITCH was delivered before the long shutdown of successful. The mass and half-life 2013, last winter’s shutdown was shortened measurement of 82Zn with ISOLTRAP is a and physics runs started up successfully at result of importance both for nuclear the beginning of April, with REX getting into structure and for astrophysics. On the laser the action during the first week of May. In spectroscopy front COLLAPS was used to the coming months up until the first week collect new data on the spins, radii, and of December, we will witness experiments moments of light 63-70Ga, neutron-rich 51K, with devices new to ISOLDE, including the and heavy Cd isotopes, while CRIS obtained active target MAYA from GANIL, an optical the first laser-spectroscopy results on TPC from Poland and the realization of the neutron-deficient Fr isotopes, opening a first resonant scattering experiments path towards laser spectroscopy with very making use of the reaction chamber weak beams. MINIBALL studied Coulomb provided by our Swedish colleagues. Last excitation of 98Sr, 128Cd, and light Pb November, two new research fellows were isotopes, and two-neutron transfer hired for ISOLDE, Susanne Kreim for reactions on 66Ni and 72Zn, extending to ISOLTRAP and Elisa Rapisarda for these heavier nuclei the methods developed MINIBALL. Jan Kurcewicz, a fellow funded in previous years and preparing to take by the ENSAR contract, who joined ISOLDE advantage of the capabilities of HIE- last December is devoting a large part of his ISOLDE. Beautiful COULEX results on time to the upgrade of the data acquisition octupole collectivity were obtained for 220Rn at ISOLDE. and 224Ra, post-accelerated beams unique HIE-ISOLDE is rapidly becoming reality as to REX-ISOLDE. The solid state studies civil engineering work started last year. The covered diffusion in semiconductors and entrance to the hall has been moved and metallic compounds and online emission- the cryo-plant and ventilation buildings are channelling studies using 27Mg and 65Ni as taking shape. Performance of the sputtered probes. Perturbed angular correlation was cavities is reaching the design goal. The used in biophysics studies with 199mHg on move of the TSR storage ring from proteins and bacteria, and for local probing Heidelberg to ISOLDE was presented to the on graphene and fullerenes. Mössbauer INTC through a detailed TDR which was spectroscopy on 119In clarified some enthusiastically endorsed. We now have to conflicting results in the literature, while Tb lobby for approval of funding for the isotopes from ISOLDE were tested for necessary building which would be located diagnosis and therapy at PSI. Several behind the ISOLDE hall on the “Jura side”. ISOLDE results were published in letter The group of the University of York has journals including the charge radii secured a used MRI solenoid which could

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form the basis of a light particle development of our science at CERN. I am spectrometer for transfer reactions, akin to pleased to leave the Physics group in the the HELIOS experiment at Argonne. After expert hands of Maria J. G. Borge, who will the summer the INTC will call for proposals take on the exhilarating and challenging for the first stage of HIE-ISOLDE at 5.5 task of leading the start up of the HIE- MeV/u. We expect an overwhelming ISOLDE physics program. I will continue to response from scientists from our 15 serve ISOLDE as chairperson of the collaboration states, including our most Collaboration Committee and look forward recent and largest member India, which to following the continued progress of this signed the ISOLDE MOU during a dedicated world class facility! workshop organised in Kolkata in April. The long shutdown will present an Yorick Blumenfeld opportunity to reflect on our long term future, and to get involved in related Information for Users: initiatives. In its long range plan published in 2010, NuPECC endorsed the construction Responsibilities of Spokespersons of EURISOL as the most important long term priority for low energy nuclear physics This year we have several new groups in Europe. You may not be aware that leading ISOLDE experiments. Let us use this ISOLDE and CERN, after having been opportunity to remind you that being a among the major players of the EURISOL spokesperson of an ISOLDE experiment Design Study, rapidly acted on this carries with it some responsibilities. recommendation. We are leading the Please make sure that all necessary EURISOL-NET network in ENSAR, a work equipment to perform your experiment is package in the TIARA preparatory phase transported in time to ISOLDE or is reserved contract devoted to designing a test stand for you at ISOLDE (electronics, power for the EURISOL high power target and this supplies, detectors, roughing and turbo month was the first meeting of a broad pumps, mechanical tools, vacuum collaboration which has formed around an elements). Contact us in advance if you initiative taken by our target group to build require any of the common equipment. and test a Pb-Bi loop at ISOLDE. Whether There were recently complaints from EURISOL is eventually sited at CERN or several fixed experiments that they were elsewhere, it will only succeed with a major used as a pool of equipment for other investment of the ISOLDE user community setups. and technical groups. Please consider Once your experiment is scheduled, check attending the EURISOL topical and town who will participate in it and whether their meetings in Lisbon in October to learn institute is part of your proposal (which can about the ongoing initiatives and be verified via Greybook). If it is not, demonstrate your support for our future contact Jenny at the ISOLDE User Support facility. Office and enquire how to add the institute This is the last time I write the introduction to your experiment. Otherwise your to the newsletter as I will be returning to colleagues will not be able to register. You Orsay in August. I thank all of you for can use this graphic “ISOLDE access” file as making my time at ISOLDE so exciting and guidance. enriching. I have done my best to Make sure that all participants of your contribute to ensuring the recognition and experiment know the rules for registering as

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CERN user and are aware of the Free CERN bike and car sharing requirements for obtaining a dosimeter and then access to ISOLDE. Again, the graphic A new bike sharing scheme allows using “ISOLDE access” should be a good start. free-of-charge bicycles even in the summer Also, the participants should have at least a peak season. The bikes are stationed in basic knowledge of ISOLDE and each shift front of the CERN reception and can be should be led by somebody with a used between 8h and 19h. When you show reasonable knowledge of the facility a proof of accommodation outside CERN (preferably somebody who recently followed you can also use them overnight to get to an ISOLDE separator course). Such a “shift your hotel. For details, check here. leader” is the person communicating with The free-of-charge CERN car sharing the ISOLDE and booster operators. scheme is now available for all CERN employees and users. There are 13 Registration and access to locations where the cars are available and ISOLDE the rental can now take place inside and outside the working hours. It might help As mentioned in the previous section, our you move around and between the CERN graphical “ISOLDE access” contains a sites. However, “the use for personal summary of how to register as a CERN user purposes, such as travel between the place and how to obtain access to ISOLDE. of residence and the work place, is strictly Important reminder: the minimum period of prohibited”. Thus, you cannot take the car your registration has to be one month, even to go to your hotel. Check here for details. if you stay only for a few days. Magdalena Kowalska Accident insurance News on data acquisition If you require an additional accident-at- software and hardware work insurance, there are two affordable offers that covers the risk of death and The Isolde DAQ based on XIA DGF-4C disability (they do not cover medical CAMAC modules is operated now from a expenses). These are the HELSANA new computer (pcepisdaq5). The new node insurance and UNIQUA Accidenta. offers a much higher operation speed and sufficient disk space. CERN Hostel booking A new oscilloscope LeCroy Wave Jet 354 is available for general use. It offers a 500

MHz bandwidth and up to 2 GS/s sampling Following last years problems with CERN rate (interleaved). The device has four input hostel availabilities, for this year we have channels (Input Impedance 1 MΩ ± 1.5% || negotiated a block booking of 10 rooms 16 pF, 50 Ω ± 1.5%) and a 7.5” color available for people on shift during the full display. running period. For practical reasons, the Two VME Universal Logic Modules VULOM booking requests should be grouped by the 4B have arrived recently. The VULOM-based spokespersons and communicated to me. trigger logics replaces several crates of NIM Please use this group booking only when and CAMAC electronics used for trigger you couldn’t book the room in the regular decisions, counting and dead-time locking. way. It is possible to use them for various

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purposes by replacing logic on the FPGA. Presently the modules are being installed Experiment reports: and tested with the MBS DAQ system. The single crystal Canberra-Eurysis Ge detector equipped with a beryllium window IS413: High-Precision Mass has returned from repair and is again Measurements of n-rich Zinc available for general use. Isotopes If you wish to use any of the above equipment, contact: In 2011, the ISOLTRAP collaboration Jan Kurcewicz succeeded in performing the first mass measurement of 82Zn, the most exotic nuclide at the N=50 shell closure. The Neutron-wall major challenge in this region of the nuclear chart, contaminations from rubidium With this note we would like to investigate isotopes, was overcome by applying all the interest for using the neutron-wall of state-of-the-art purification techniques the European gamma-ray spectroscopy pool available at both, ISOLDE and ISOLTRAP: in an experimental campaign at ISOLDE At ISOLDE, instead of directly irradiating the after the long shutdown of 2013. target, a neutron converter was used, The neutron wall consists of 50 liquid furthermore a quartz transfer line scintillator detectors that can be used in a suppressed unwanted ions, and finally closely packed geometry covering a solid resonant laser ionization with RILIS further angle of approximately 1pi/sr but potentially increased the ion-of-interest to also in other geometries. In the closely contamination ratio. At ISOLTRAP (see packed configuration the distance from the report on IS 518 by M. Rosenbusch for a center of the set-up to the detector surface detailed experimental description), the is 50 cm. The thickness of the detectors is recently integrated MR-TOF mass separator 15 cm. The detectors use pulse shape [1,2] acted as the main device for discrimination in order to separate neutrons contamination removal. In contrast to the and gamma-rays. As part of the European standard cleaning in the preparation gamma-ray spectroscopy pool the detector Penning trap it allows the removal of is available for experimental campaigns at contaminations within only a few European accelerator laboratories. The n- milliseconds. The position of the center of wall is managed by the nuclear structure the resonances of 80-82Zn were determined group at Uppsala University and is currently by the conventional time-of-flight ion- located at GANIL. If you are interested in cyclotron resonance (ToF-ICR) method (Fig. learning more about the possibilities of the 1 left) and by use of the Ramsey excitation n-wall please contact Johan Nyberg at scheme (Fig. 1 right), resulting in a relative Uppsala University. If sufficient interest is uncertainty of 4*10-8. Furthermore, the life found we will submit an application to the time of 82Zn was measured by monitoring owners committee of the gamma-ray pool the decay during storage in ISOLTRAP’s first for a campaign at ISOLDE. trap, the RFQ buncher. The data are under Visit http://nsg.physics.uu.se/nwall for more evaluation. information about the n-wall or send On the one hand, the low uncertainty of 10- an e-mail to johan.nyberg at physics.uu.se 8 allows for the most exotic test yet of N=50 Joakim Cederkäll shell gap. On the other hand, the mass of

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82Zn is important in the context of stellar IS433: First data sets on 35Ar nucleosynthesis, in particular for modeling acquired with the WITCH the r-process path [3], and can be used to experiment probe the elemental composition of the outer crust of neutron stars [4]. Low energy precision experiments searching

for exotic components in the weak interaction are complementary to the high energy experiments at colliders dedicated to discover new particles. In the WITCH experiment the beta neutrino angular correlation coefficient (a) in the beta decay of 35Ar is studied to search for a possible admixture of a scalar weak interaction component. The WITCH setup [1,2] is situated behind REXtrap getting pre-cooled bunches of up to 1*106 ions. The ion bunch is transferred through the horizontal and vertical beam lines to the WITCH Penning traps. In the first trap the ion ensemble is further cooled and centered by interaction with a buffer gas environment. After transfer to the second trap the ions are stored there under UHV conditions and left to decay. In the decay process the ions receive recoil energy allowing them to leave the trap. Half of the ions travel upwards through the spectrometer where almost all their energy is converted into axial energy which is then FIG. 1: Conventional ToF-ICR (left) and analyzed by a blocking potential in the 82 Ramsey-excitation resonance (right) of Zn. retardation spectrometer. A spectrum is The red lines show a fit of the expected recorded by counting the number of ions resonance curves to the data. reaching the main detector as a function of time, i.e. voltage. [1] R.N. Wolf et al., Hyperfine Interact. 199 2011 was a very successful year for the (2011) 115. WITCH collaboration! After a first test with [2] R.N. Wolf et al., Int. J. Mass Spectrom. 124In [3], several upgrades [4-6] had been 313 (2012) 8. implemented to remove a number of [3] S. Baruah et al., Phys. Rev. Lett 101 observed disturbing effects and to improve (2008) 262501. the quality of the WITCH operations. It was [4] S. Goriely et al., A&A 531 (2011) A78. finally possible to acquire first data on the prime physics case of 35Ar. Although in a R. Wolf for the ISOLTRAP Collaboration first experiment, in June, only a few thousand counts were recorded, this still allowed reconstructing the recoil energy distribution of the daughter nuclei 35Cl. This

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very preliminary spectrum was investigated the experimental cycle. Counts are missing, with the help of software packages where a retardation voltage is applied in the developed in our collaboration [7,8]. spectrometer with respect to the Although the achieved precision on a was undisturbed exponential decay, i.e. when no still limited [9] it demonstrated the full potential is applied. These missing counts operationality of the setup. are the events, which can be attributed to A second online experiment was performed recoil ions. Since this spectrum contains at the end of October. Despite of problems more than 105 events a statistical with the ISOLDE target and with the uncertainty of less than 5% in the transmission between REXtrap and the determination of the correlation parameter WITCH cooler trap significantly higher a should be reachable. statistics was acquired. It was, however, not yet sufficient to study systematic [1] M. Beck et al., Nucl. Instr. Meth. A 503 effects. Fortunately another experiment (2003) 567. could be performed within a week due to [2] V.Yu. Kozlov et al., Nucl. Instr. and the efforts of the target group and the I88 Meth. B 266 (2008) 4515-4520. collaboration offering their time slot. [3] M. Beck et al., Eur. Phys. J. A 47 (2011)

45. 80000 600 [4] M. Tandecki, PhD thesis, IKS, KULeuven ON 70000 500 (2011).

400 60000 [5] E. Traykov et al., Nucl. Instr. and Meth. 300

Spectrometer Voltage / V 648 (2011) 1-14. 50000 OFF 200 100 [6] M. Tandecki et al., Nucl. Instr. and

40000 0 0 1 2 3 4 5 Meth. A 629 (2011) 396-405. 30000 Time / s

Counts at main detector [7] S. Van Gorp et al., Nucl. Instr. and 20000 Meth. A 638 (2011) 192-200. 10000 [8] P. Friedag, diploma thesis, IfK,

0 University Muenster (2008). 0 1 2 3 4 5 [9] S. Van Gorp et al. in preparation. Time in experimental cycle / s M. Breitenfeldt Fig. 1: Detected ions on the main detector as a function of the time in the experimental cycle. The inset shows the IS448 and I88: Metal ions in applied retardation voltage in the biology spectrometer as a function of time. Peaks in count rate are observed when no The main objective addressed in both these retardation potential is applied (‘OFF’), while projects is to explore the structural and dips indicate that recoil ions have been catalytic role of metal ions in biological blocked by the retardation voltage that was molecules. Understanding the manner in applied (‘ON’). which certain metal ions bind to their biological ligands and activate them An example of an obtained raw spectrum is structurally, allows many crucial and, as-yet shown in Fig. 1. The number of counts on unanswered/unresolved issues, to be the main detector is plotted as a function of addressed, for instance: Is the structure of time. In the inset the applied retardation a protein dictated ONLY by the amino acids voltage is given as a function of the time in sequences or is it also steered by metal ions

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– even for proteins that do not contain One of our achievements in the past year metal ions in their folded state? Studying has been in describing the Pb2(II) the biochemistry of the most abundant coordination compound: [AsPh4]4[Pb(i- metal ions in biology is actually as important mnt)4]. The measured spectrum shown in as elucidating the toxicity of heavy metal Figure 1 represents the very first application ions, such as Hg(II), Pb(II) and Cd(II) at of 204mPb-PAC to a Pb(II) molecular crystal the molecular level. For the latter elements with a known structure [1]. Electronic these matters can be addressed using PAC structure calculations (DFT), determined at Spectroscopy. This technique cannot, the PW91/QZ4P level including relativistic however, stand alone and always has to be effects using the two-component zeroth- supported by other complementary order regular approximation method, agree techniques, such as UV-Vis, CD, NMR, reasonably well with the experimental data EXAFS and fluorescence spectroscopies, as for the dimeric structure (Figure 2 right) but well as by quantum mechanical calculations not monomeric as previously reported in the of spectroscopic properties. literature (Fig 2 left). Our findings are providing valuable information on the coordination chemistry geometry of Pb(II), and thus contributing to a better understanding of how and where the lead ion binds to bio-molecules.

Fig 2. Models of [AsPh4]4[Pb(i-mnt)4]. Reprinted with permission from [1]

The second of our projects, I88, aims to set up the world's first β-NMR instrument designed for biophysics applications. β-NMR is a technique where NMR resonances are observed as changes in the β decay anisotropy. It has already been successfully applied in solid state and nuclear physics and the technique also holds great promise

Fig 1. 204mPb-PAC spectra of powder for successful applications in biology, crystals of [AsPh4]4[Pb(i-mnt)4] (blue line: although no such experiment has yet been experimental data, black line: fit). Reprinted performed on soft matter. The underlying with permission from [1] basic physics is the same as for NMR spectroscopy on stable isotopes, thus,

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knowledge built up over the last decades for pin-holes. For this year's run, however, we NMR may be transferred to β-NMR believe we can improve the experimental applications. This project is motivated by conditions by using so-called ionic liquids as the need to find a new spectroscopic our targets, which have negligible vapor approach to study electronically and pressure and therefore are ideal for our magnetically silent metal ions, such as purpose. Mg(II), Ca(II), Zn(II) and Cu(I), some of the most essential ions in biology. [1] Vibenholt et al, “Application of 204mPb Perturbed Angular Correlation of γ-rays Spectroscopy in Coordination Chemistry” accepted for publication in Inorganic Chemistry, 2012

M. Stachura on behalf of IS448, IS488 and I88 collaborations

IS453: Minority-site occupancy of transition metals in dilute magnetic semiconductors

For the EC-SLI collaboration, 2011 marked the end of an important chapter on the lattice location of transition metals in dilute magnetic semiconductors. Unexpected results from the experimental runs of 2007- 2009, which required careful validation by experiments performed in 2010, finally came together in several publications (two of which were already published [1,2]). In a dilute magnetic semiconductor (DMS), magnetic atoms (or impurities) are Fig 3. The bio-setup at the COLLAPS introduced in an otherwise non-magnetic magnet semiconductor. For almost two decades, the co-existence of ferromagnetism and In November 2011 the first on-line tests semiconducting behavior in some DMS with a stable Mg(II) beam took place, in materials has generated fundamental new which we demonstrated a fully working and physics and enabled the study of ready-for-radioactive-beams experimental phenomena of interest for spin electronics setup. The system, illustrated in Figure 3, (spintronics) [3,4]. The current research was assembled at ISOLDE and tested at the interest can be narrowed down to two main COLLAPS beam line. The tests showed that classes of materials: (1) narrow-gap III-V the sole remaining issue is low beam semiconductors, mostly GaAs, doped with transmission through the array of 3x4mm Mn; (2) wide-gap oxides and nitrides doped

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with 3d transition metals, mostly Mn-, Fe- and Co-doped ZnO and GaN. However, even these intensively studied DMS materials are still far from understood [4]. Some of the open questions are at the very basis of the DMS magnetism: the position (site) of the magnetic impurities in the host lattice. In general, it is easy to determine the lattice site occupied by the majority of the impurities. It is, however, far more challenging to identify lattice sites occupied by minority fractions which can, nevertheless, dramatically affect the magnetic behavior of the DMS. Emission channeling (EC) overcomes several limitations of conventional techniques used to determine the lattice location of impurities in semiconductors. For β- EC experiments performed with the short-lived isotopes 56Mn (2.58 h) and 61Co (1.6 h), IS453 makes use of the on-line EC- Fig. 1: (a)-(d) Normalized experimental SLI setup, presently coupled to the GHM emission channeling patterns (undoped beam line. While 56Mn is available directly, GaAs) in the vicinity of the <100>, <111>, 61Co is obtained by implanting the short- <110> and <211> directions following lived precursor isotope 61Mn and exploiting annealing at 100ºC. (e)-(h) Corresponding 61 61 best fits yielding 70% and 30% of the Mn the decay chain Mn (4.6 s) → Fe (6 min) 61 atoms on Ga-substitutional and As- → Co. In 56Mn-implanted GaAs, in addition to the tetrahedral interstitial sites, respectively. majority substituting for Ga, we identified a 56 61 significant fraction of the 56Mn impurities In Mn- and Co-implanted ZnO and GaN, occupying tetrahedral interstitial sites with in addition to the majority substituting for the host cations (Zn in ZnO and Ga in GaN), As nearest neighbors (Figs. 1 and 2a) [1]. The interstitial fraction is stable up to we identified significant fractions of the 400ºC, with an activation energy for impurities occupying substitutional anion diffusion of 1.7–2.3 eV [1]. Substitutional sites (O in ZnO and N in GaN), which are 56Mn becomes mobile at higher virtually unaffected by thermal annealing up temperatures (~700ºC), with an activation to 900ºC [2] (Fig. 2b). Anion substitution by energy of ~3 eV. Being difficult to reconcile Mn and Co impurities in wurtzite ZnO and GaN, which had never been observed with the general belief that interstitial Mn out-diffuses at ~200ºC with an activation before, challenges our understanding of energy of ~0.7 eV [5,6], our findings have transition-metal incorporation in wide-gap oxides and nitrides. profound implications on the prospects for achieving higher Curie temperatures in Mn- The magnetism community received very doped GaAs, one of the major goals in the well the results of these two sets of DMS field [4]. emission channeling experiments. For an oral communication compiling these findings, Lino M. C. Pereira* won the "Best

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student presentation award" at the 56th IS463: Study of neutron- Annual Conference on Magnetism and deficient Tl isotopes Magnetic Materials (November 2011, Scottsdale, USA), one of the most important Exotic ion beams produced at ISOLDE often conferences on magnetism and magnetic consist of the ions of interest as well as materials. isobaric and isomeric contaminations. Thanks to its high resolving power of up to 106 the Penning-trap mass spectrometer ISOLTRAP [1] is able to resolve isomeric states even below 100 keV (for A ≥ 150) and thus can provide pure ion ensembles adequate for decay studies. Therefore, a trap-assisted decay spectroscopy setup was

developed and installed at the end of the

ISOLTRAP beamline [2]. It consists of an

aluminized Mylar tape that is surrounded by

a thin plastic scintillator sensitive to beta particles. Furthermore, two high-purity germanium detectors for gamma detection are in close proximity. All events are recorded by the ISOLDE digital data acquisition system allowing off-line reconstruction of coincidences. Fig.2:(a) Ga-substitutional and As- In 2010, a series of mass and decay 56 measurements was performed to study tetrahedral (TAs) interstitial fractions of Mn isomerism in the neutron-deficient thallium in GaAs of different doping types. (b) Cation 193-195 and anion substitutional fractions of 56Mn isotopes Tl. During this beamtime, the 61 excitation energy of the first isomeric state and Co in ZnO and GaN. 194 in Tl was determined for the first time *PhD student at IKS (KU Leuven) and IN- and the spin assignment of ground and IFIMUP (University of Porto) until December isomeric state was confirmed. In 2011, 2011; currently a postdoctoral fellow at IKS. ground and isomeric state in the even more exotic isotope 190Tl were investigated. It is [1] L. M. C. Pereira et al., Appl. Phys. Lett. (-) (+) 98, 201905 (2011) known that there exist a 2 and a 7 state [2] L. M. C. Pereira et al., Phys. Rev. B 84, that differ in their decay pattern but their 125204 (2011). assignment to the ground and first isomeric [3] A. H. Macdonald et al., Nature Mater. 4, state is still not clear. During this run, the 195 (2005). mass of one of the states was determined with high precision and via the decay [4] T. Dietl, Nature Mater. 9, 965 (2010). (+) [5] K. W. Edmonds et al., Phys. Rev. Lett. pattern the 7 state was assigned to it. A 92, 037201 (2004). γ−γ-coincidence spectrum of the two [6] T. Jungwirth et al., Phys. Rev. B 72, germanium detectors at the implantation 165204 (2005). point is shown in Fig. 1. U. Wahl, J.G. Correia, L. Pereira

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In addition to the information provided by hyperfine measurements, decay spectroscopy can supply us with detailed information about the isomeric structure of 202,204Fr and its beta-delayed fission process.

Fig. 1: 190Tl γ-γ-coincidence spectrum between the two high-purity germanium detectors at the implantation point. Figure 1: 3D drawing of the CRIS beam [1] M. Mukherjee et al., Eur. Phys. J. A, line and the decay spectroscopy station. 2008. [2] M. Kowalska et al., submitted to Nucl. Figure 1 shows the CRIS beam line where Inst. and Meth. A, 2011. laser radiation is used to step-wise excite and ionize an atomic beam using its J. Stanja for the ISOLTRAP Collaboration characteristic hyperfine structure. In addition to hyperfine measurements, this technique offers the ability to purify an ion IS471: Collinear resonant beam that is heavily contaminated with radioactive isobars, including the ground ionization laser spectroscopy of state of an isotope from its isomer [2], rare francium isotopes allowing decay spectroscopy to be performed. In November of 2011, the CRIS beam line A 30 kV bunched ion beam from HRS was at ISOLDE performed its first collinear deflected down the CRIS beam line and resonant ionization laser spectroscopy on 207 neutralized by a potassium Fr. This experiment marks the successful vapour charge exchange commissioning of the beam line [1]. A new cell, with an efficiency of decay spectroscopy station was also ~50%. A scanning voltage developed, and laser assisted decay was applied to the spectroscopy was demonstrated in a neutralization cell, varying collinear geometry. the velocity of the bunch, This is the first experiment in a campaign to tuning it onto resonance address several questions arising in the with the laser. The francium isotopes: the possible onset of resonantly produced ions shape coexistence in neutron deficient were then deflected and francium isotopes, the magnetic moment -1 + detected with a MCP, or and isomer shift of the (πs1/2 )½ intruder implanted in C-foils in the state in 201,203Fr and the boundary of the 218,219 decay spectroscopy station. region of reflection asymmetry in Fr. The ionization scheme for

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francium consisted of a resonant (422nm) The collinear geometry of the CRIS beam 2 step from the 7 S1/2 ground state to the line gives a reduction in thermal Doppler 2 3 8 P3/2 excited state [3], followed by a non- broadening by a factor of ≈10 , thus the resonant 1064nm step into the continuum. selectivity of the state of interest is greatly A new laser system was developed for this increased. The narrower line widths of the purpose based on a tunable diode laser, hyperfine transitions produced by the which is pulsed amplified in a TiSa crystal geometry lead to a greater degree of [4]. The system was pumped by a 10Hz selectivity between the ground state and Nd:YAG laser, which was also used to isomeric state of the isotope; thus decay provide the 1064nm ionization step. The spectroscopy on pure isomeric states can be collinear resonant ionization spectrum of achieved. 207Fr can be seen in Figure 2. From a preliminary analysis of the experimental data, a value for the ground- state A-factor of A(S1/2)=8390(100)[200] MHz was found, which compares well with the literature value of A(S1/2)=8484(1) MHz [5]. The lower resolution obtained in this first run was due to power broadening of the 422 nm resonant step, which occurred while trying to optimize the overall experimental efficiency. In future experiments, this should be reduced, and the ionization efficiency should be enhanced by increasing the laser power of the 1064 nm non-resonant step by several orders of magnitude. Figure 3: Alpha spectrum of the laser assisted decay spectroscopy performed on 207Fr.

Laser assisted decay spectroscopy was successfully performed on 207Fr during the IS471 run. Figure 3 shows the increase in the number of alpha particles detected when the laser was on resonance (blue spectrum) compared to when it had been blocked (red spectrum). The characteristic alpha particles emitted from 207Fr and its daughter 203At can be seen, giving an overall increase of a factor of 20 when the lasers are on. However, this result masks the low background rate (associated with Figure 2: Collinear resonant ionization collisional non-resonant ionization) due to spectrum of 207Fr. Solid red line shows the the UHV conditions within the interaction fit to the experimental data. region. The red line in Figure 3 could be further reduced by an order of magnitude by improvements in the vacuum (through

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baking) to 10-9 mbar; and additionally, the decay would lead to a determination of the blue line could be increased by an increase unknown neutrino mass. in the resonant ionization efficiency. One key parameter in the design of a The coming year will be spent improving double-beta decay experiment is the Q the ion beam transport and resonant value of the transition, i.e. the mass ionization efficiencies and then completing difference between the mother nuclide and the study of the francium isotopes. The the daughter nuclide. Its value defines the isotopes 201-206,218,219Fr will be studied with position of the characteristic single peak in collinear resonant ionization spectroscopy; the beta energy spectrum. Very few events along with a detailed study with laser are expected and thus, a precise assisted decay spectroscopy of the isomers determination of the Q value is of utmost in 202Fr and 204Fr. importance to discriminate the signal from the background. [1] J. Billowes et al. CERN-INTC-2008-010. Only eleven nuclides have Q values high INTC-P-240 CERN, Geneva (2008) enough to allow the neutrinoless double- [2] V. Letokhov Opt. Commun. 7 59 – 60 beta decay energetically and to reduce the (1973) expected half-life below the experimental [3] H. T. Duong et al. Eurphys. Lett. 3 175 limit. At the Penning trap mass (1987) spectrometer ISOLTRAP [2] at ISOLDE, the [4] M. Hori and A. Dax Opt. Lett. 34 1273 Q value of the candidate with the highest (2009) natural abundance, 110Pd, was determined [5] A. Coc et al. Phys. Lett. B 163 66 with unprecedented accuracy. (1985) The experimental setup consisted of the two ISOLTRAP Penning-traps and a laser- The authors would like to acknowledge the ablation source [3] for the off-line ion ISOLDE technical staff for their assistance production of the mother nuclide 110Pd+ and during the experiment. its daughter nuclide 110Cd+. Palladium and cadmium foils were mounted on a rotary K.M. Lynch sample holder to easily switch between the two isotopes. A 10 Hz frequency-doubled IS473: Q value for the double- Nd:YAG laser was focussed on the samples 110 for ablation and ionisation. The ion bunch beta decay nuclide Pd was then purified by the preparation

Penning trap with buffer-gas cooling and The hunt for the first detection of the sent to the precision Penning trap, where neutrinoless double-beta decay is one of the the Ramsey time-of-flight ion-cyclotron most ambitious endeavours in particle resonance detection technique [4] was physics [1]. Since the nuclide would decay applied to determine its cyclotron by emitting only two electrons, the process frequency. See contribution of M. would violate the law of lepton number Rosenbusch for further details of the conservation and is thus forbidden by the experimental setup. An example of an Standard Model of particle physics. On the 110Pd+ resonance is shown in figure 1. other hand, it would only occur if the The Q value was determined from the neutrino is its own antiparticle; a so-called cyclotron frequency ratio of 110Pd+ and Majorana particle. In addition, an 110Cd+ to be Q = 2017.85(64) keV [5]. This observation of the neutrinoless double-beta

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IS475: Octupole Collectivity – Coulomb Excitation of 224Ra and 220Rn

The physics overview for this experiment was set out in last years ISOLDE Newsletter (2011) [1]. The aim of the experiment was to ascertain the strength of octupole correlations by measuring the E3 moments in nuclei where they are expected to be largest i.e. at Z = 88 and N = 134. Here,

there are a lack of spectroscopic data and Figure 1: Ramsey time-of-flight resonance 226 as a function of the excitation frequency for so far, only for Ra, with its comparatively 110Pd+ with a fit of the expected line shape long half life of 1600 years, has it been (solid line). possible to measure the B(E3) strength using Coulomb excitation [2]. value is shifted by 14 keV compared to the Using the unique capabilities of ISOLDE to previous literature value [6] and has a 17 produce high intensity radioactive ion times lower uncertainty. The new value is beams in the mass A=220 region, and the accurate enough to allow future ability of REX to accelerate these ions to experiments on neutrinoless double-beta 2.83 A.MeV, 224Ra was Coulomb excited by decay to distinguish the experimental signal 112Cd and 120Sn secondary targets in inverse from the background. Moreover, the more kinematics in 2010. The collaboration precise Q value lead to a recalculation of returned in 2011 to study 220Rn at 2.82 the phase-space factors of the neutrinoless A.MeV using 60Ni, 114Cd and 120Sn secondary double-beta decay and its competing targets. neutrino-accompanied mode, and thus to a The use of a much lighter target (changing new evaluation of both double-beta decay Z from ~50 to Z=28) meant a significant half-lives of 110Pd [5]. change in the population of the states of

References: interest in the nucleus, as can be seen in [1] K. Zuber, Contemp. Phys. 45, 491 Figure 1. The lighter target reduces the (2004). Coulomb excitation cross-section for [2] M. Mukherjee et al., Eur. Phys. J. A 35, second-order processes and this allows one 1 (2008). to disentangle the various excitation paths [3] K. Blaum et al., Eur. Phys. J. A 15, 245 in the analysis, leading to a more precise (2002). measurement of the E2 and E3 matrix elements. [4] S. George et al., Phys. Rev. Lett. 98, 220 162501 (2007) A new state was observed in Rn for the [5] D. Fink et al., Phys. Rev. Lett. 108, first time at 939keV. A similar state is also populated in 224Ra, which was previously 062502 (2012) + [6] G. Audi, A. H. Wapstra, and C. Thibault, observed in β-decay measurements as a 2 Nucl. Phys. A729, 337 (2003). state, at 965keV. It is proposed that this is a 2+ member of the K=2, γ-band. Its placement in the level scheme can be D. Fink for the ISOLTRAP collaboration confirmed using γ-γ coincidences in the MINIBALL array.

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IS477: Coulomb Excitation of 128Cd

The cadmium isotopic chain remains to be one of the most interesting in modern nuclear structure physics as it is 48 protons and, therefore, two proton holes below the Z=50 shell closure. Coulomb excitation experiments performed at REX-ISOLDE measured for the neutron-rich isotopes 122Cd, 124Cd, and 126Cd enhanced + + Figure 1: MINIBALL spectrum showing de- B(E2;0 →21 )-values [1]. A striking anomaly excitation gamma rays, background has been observed for the excitation energy subtracted, from 220Rn after Coulomb of the first excited 2+-state in 128Cd (N=80). excitation with 120Sn (Blue) and 120Sn (Red; Contrary to the expectations of a steady normalised to 2+ → 0+) target at 2.82 increase towards the semi-magic isotope A.MeV. One can see how the relative 130Cd, it is found at a lower energy population of the states of interest (2+, 4+, compared to the corresponding excitation in 3-) changes when varying the mass of the 126Cd [Fig.1]. target. Following this success of using the lighter, 60Ni target, we ran for 1 extra day with 224Ra in 2011 on 60Ni. As with the 2010 campaign, we were able to utilise the “offline” mode of ISOLDE after the protons were no longer impinged on the primary target. Preliminary analysis using the GOSIA code [3] shows that the collective behaviour of 224Ra is very similar to that of 226Ra. A strong E3 matrix element connects the ground state to the first 3- showing enhanced octupole collectivity. Analysis of 220Rn is still on going, but there is significant population of the negative parity states + indicating a strong E3 coupling to the Fig.1: Excitation energy of the first 2 -state ground state. for different nuclei.

References: Currently, only a Beyond Mean Field [1] L. P. Gaffney et al., “Contributions to approach is capable to reproduce these Research at ISOLDE in 2010”, (2011) IS475 findings [2]. However, these calculations [2] H. J. Wollersheim et al., Nucl. Phys A must assume an already considerable 556, (1993) 261 prolate deformation. This raises the [3] T. Czosnyka et al., Bull. Am. Phys. Soc. question about the degree of quadrupole 28, (1983) 745 collectivity for this particular nucleus. The relevance of that question is underlined by L. Gaffney

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the close proximity of this nucleus to the primary production to the secondary target, waiting point 130Cd of the astrophysical r- a fraction of the interesting nuclei decays process which was found to be a typical already in flight. This accounts partly for the closed shell nucleus [3]. A measure for the isobaric beam contaminants, such as 128In + + 128 quadrupole collectivity is the B(E2; 0 →21 ) and Sn. Furthermore, the volatile, easily reduced transition probability. This quantity ionized 128Cs was identified as beam is accessible via Coulomb excitation and the contaminant. The beam composition was + + extraction of the B(E2; 21 →0 )-value from disentangled using the ΔE-E information the excitation probability. Therefore, post- obtained with an ionisation chamber and a accelerated 128Cd projectiles are shot on a silicon telescope, as well as the known scattering target. Proportional to the E2- radioactive decay behaviour. The latter has excitation probability the nucleus will been recorded in the beam dump and in exchange a virtual photon with one of the short runs using a thick 64Zn stopper target target nuclei resulting in excited nuclei. (14.89 mg/cm²). Obviously, a sufficient number of projectiles, representing a statistically relevant ensemble, are required to measure the cross section of this reaction. ISOLDE represents worldwide the only radioactive beam facility capable to provide this rare isotope in sufficient quantities, so that a post-accelerated beam can be investigated with this versatile experimental tool. The corresponding experiment on 128Cd was performed in August 2011 exploiting the outstanding production yield achieved at Fig.2: Doppler-corrected gamma-spectrum ISOLDE in combination with the unique with a clear peak at 648 keV stemming from capability of a selective ionisation scheme + + 128 the 21 → 0 transition in Cd. (RILIS) and REX to post-accelerate these rare radioactive ion beams. In the 128 Fig. [2] shows the Coulomb excitation γ-ray experiment a beam of Cd with an energy spectrum recorded in a total beam time of of 2.85 MeV/nucleon was delivered to the 64 ~50 hours. To create this spectrum a detection setup. A Zn (1.48 mg/cm²) Doppler correction with respect to the target was used to Coulomb excite the 128 beam-like particles and random background impinging Cd nuclei. Both the scattered subtraction were performed. The 648-keV projectile and recoiling target nuclei were + + peak corresponds to the interesting 21 →0 detected using a double-sided silicon strip transition. With an analysis performed detector (DSSSD). The de-excitation γ-rays relative to the target excitation (at an following the Coulomb excitation were energy of 991 keV) and the information detected by the highly efficient MINIBALL about the beam composition as well as the spectrometer consisting of 24 HPGe number of γ-rays detected for the 648-keV detectors. Apart from the low intensities, + + 128 128 peak of the 21 →0 transition of Cd will the short halflife of Cd (T1/2 = 340 ms) is + + allow the extraction of the B(E2;0 →21 )- one of the major challenges. Owed to the value in the ongoing analysis. time needed for charge-breeding and transport of the isotope of interest from the

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References: 1 ns) in the 119 K – 92 K temperature [1] Th. Behrens, PhD Thesis, Technische range while no change is observed in the Cd Universität München, 2009 local environment (see Fig. 1.). [2] T. Rodriguez et al., Phys. Lett. B 668, The temperature dependence of lattice (2008) 410 parameters, [a(T)], obtained from PDFs [3] A. Jungclaus et al., Phys. Rev. Lett. 99, refinements are depicted in Fig. 2 (top) 132501 (2007) shows three distinct regimes in the temperature range 80-220 K. For T>130 K, S. Bönig, Th. Kröll, M. Scheck a(T) displays a conventional linear

contraction on cooling. A change of this IS487: Cr3+ Dynamic off- monotonic trend occurs at TF~130 K where an expansion regime sets in. The centering in CdCr2S4 leading to temperature dependence of the amplitude Magnetic-electric Clusters of the off-centering displacements (Δr) is displayed in Fig. 2 (bottom) where a The cubic spinel CdCr2S4 gained recently a maximum value of 0.011 Å was obtained. vivid interest, given the relevance of relaxor-like dielectric behavior in its paramagnetic phase. By a singular combination of local probe techniques namely Pair Distribution Function (PDF) and

Figure 2: Temperature dependence lattice parameters (top). Amplitude of the Cr local off-centering (bottom).

We further show that this off-centering of Figure 1: Representative R(t) functions the magnetic Cr-ion gives rise to a peculiar taken at different temperatures. entanglement between the polar and magnetic degrees of freedom, stabilizing, in Perturbed Angular Correlation (PAC) we the paramagnetic phase, short range firmly establish that the Cr ion plays the magnetic clusters, clearly seen in ultra-low central key role on this exotic phenomenon, field susceptibility measurements in the namely through a dynamic off-centering form of step-like behaviour in temperature displacement of its coordination sphere. range between the ordering temperature PAC measurements, can infer that the Cr TC~86 K and TPM~116 K. This feature in site experiences an ultra-slow dynamics (τ> the paramagnetic (PM) regime is a

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fingerprint of the presence of short-range χ−1(T) measured on heating and with H = magnetic clusters (see Fig. 3 left). Landau 103 Oe. right: χ−1(T) resulting from theory demonstrates the role of a linear theoretical calculations of the phase coupling between the magnetic and polar transitions Landau theory, considering linear order parameters on the appearance of magneto-electric coupling. magnetic cluster in paramagnetic phase of this compound (see Fig. 3 right). We speculate that this Cr3+ dynamic off- This new discovery and interpretation open centering is intrinsically entangled to the insights on the hotly debated magnetic and formation of local dipoles, which are polar interaction, setting a step forward in responsible for the observed magnetic the reinterpretation of the coupling of correlations between adjacent Cr3+ different physical degrees of freedom. neighbours. We further confirm this electric In summary, our PDF, PAC and M(T) and magnetic orders entanglement by experimental findings prove the existence of modeling the peculiar low-field χ−1 (T) a dynamic state caused by the presence of measurements via Landau theory using a simultaneous polar and magnetic linear magneto-electric coupling. nanoclusters, pointing to the birelaxor nature of the system. Our results are G. Oliveira consistent with a picture where the effects described in the recent literature arise from IS489: New online diffusion Cr3+atomic displacements occurring well above the magnetic ordering temperature. setup comes to ISOLDE Our combined analysis clearly shows that the increasing of the average size of The application of radioactivity in solid state random oriented dipoles or polar physics dates back to the early days of nanoclusters saturates at TPM, nuclear physics. The first such application of concomitantly with the onsets of their “tracer methods” was by van Hevesy in the dynamic slowing down and Cr3+-Cr3+ early 1920s to investigate self-diffusion in magnetic correlations. We also show that an Pb [1]. Studying diffusion in solids by ultra slow Cr3+ - exploiting radioactive isotopes remains one of the most efficient means of exploring - m phase diffusion processes with high sensitivity, in transition pointing to its order-disorder type particular allowing the ability to study self- origin. diffusion in a relatively straightforward way. Furthermore, the possibilities of exploring diffusion processes using radioactivity are greatly enhanced when coupled to an isotope factory such as ISOLDE. The principles behind radiotracer diffusion have remained essentially unchanged since the earliest experiments: radioactivity is introduced into a sample – in the case of ISOLDE via implantation – then thermal treatments allow the radioactive isotopes to diffuse into the material. The sample is then −1 Figure 3: left: χ (T) with different “sliced” – usually using a polishing applied magnetic fields 1-101 Oe; Inset: apparatus – and, by measuring the activity

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of the resulting slices, allows a diffusion the on-board furnace; sectioning of the profile to be determined. A very active sample is achieved using an Ar+ ion gun programme exploring diffusion has already and a tape station catches the sputtered been underway at ISOLDE for many years activity and transports it to a Ge detector and in recent times has focussed on the where the gamma spectrum will be anomalous diffusion profiles seen in measured. The initial tests at LA1 in 2011 compound semiconductors such as were promising and the chamber will now CdTe[2,3]. A limitation of the technique be semi-permanently installed at the GLM until now has been that half-lives of about 1 beam line in early 2012, where “parasitic” hour and below have been out of collections will be possible in addition to the experimental reach. This has meant that well-defined programme of IS489. The some highly interesting cases such as combination of ISOLDE – with its range of magnetic dopants in semiconductors and beams – and this unique chamber should long-standing questions such as self- make for a very exciting physics run in diffusion in Al have been tantalisingly 2012. excluded from the experimental programme. References: [1] J. Gróh and G. v. Hevesy, Ann. Phys., 65, 216 (1921). [2] H. Wolf, F. Wagner, Th. Wichert, and ISOLDE Collaboration, Phys. Rev. Lett. 94, 25901 (2005). [3] H. Wolf, J. Kronenberg, F. Wagner, Th. Wichert, and Isolde Collaboration, Pre-requisites for the formation of unusual diffusion profiles in II-VI semiconductors, Phys. Status Solidi B 247, 1405 (2010).

K. Johnston

Figure 2 Installation of the new online IS496: First measurement of the diffusion chamber at ISOLDE in 2011. + + 140 B(E2;2 1→0 1) value of Nd However, in summer 2011, an online st th diffusion chamber which will allow these From July 1 to July 4 , 2011, the first part isotopes – among others – to be finally of experiment IS496 was performed with studied was delivered to ISOLDE and the Coulomb excitation of radioactive, 140 installed and tested at LA1. This chamber proton-rich Nd nuclei at MINIBALL. The incorporates all the basic elements of a final goal of the full IS496 experiment is the traditional radio-tracer apparatus as study of the effect of shell stabilization of described above, but every step will be the collective isovector valence-shell carried out in situ, without breaking the excitations along the N=80 isotonic chain vacuum. The sample will be implanted using [1,2]. As a first step the B(E2) value of the the ISOLDE beam; thermal treatments (up first excited 2+ state of 140Nd was to 1600 °C) to trigger the diffusion will be measured, which is essential for the carried out by transporting the sample into interpretation of further data, to be taken in

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2012 for 142Sm and in 2014/2015 at HIE- ISOLDE for both isotopes, where also the investigation of higher-lying (mixed- symmetry) states is foreseen. The RILIS ion source and its newly developed ionization scheme for Neodymium was used in combined laser- on/laser-off runs in order to estimate the fraction of 140Nd ions in the beam besides the main contaminant 140Sm. Data was taken for almost 60 hours at an average current of 1-2 pA. Two different targets, 48Ti and 64Zn, were used for projectile-Coulomb excitation reactions. The beam energy was constant at 2.85 MeV/u. Figure 1 shows the random-background subtracted Coulomb- excitation spectra, Doppler-corrected for beam particles with A=140 as well as for target excitation. The gamma-ray spectra are dominated by the decays of the first 2+ states of 140Sm, 140Nd and 48Ti, respectively. The Coulomb excitation cross-section of 140Nd has been normalized to the Figure 3: Doppler-corrected γ-ray excitations of the targets. A conclusive spectra after subtraction of random analysis with the multi-step Coulomb- background. The Doppler correction was excitation code GOSIA [3] uses various done with respect to the projectile (top, ranges of scattering angles, covered by the middle) or target nuclei (bottom). The CD-shaped particle detector. The laser ionization was used for the top and + + preliminary result for the B(E2;2 1→0 1) bottom spectra. value of 140Nd is 30(5) W.u. representing first information on that quantity. 122501 (2006) This value is larger than expected from QPM [3] T. Czosnyka et al., Bull. Am. Phys. Soc. calculations for N=80 isotones, that yield 17 28, 745 (1983) W.u. [4], only. The calculations need to be [4] Ch. Stoyanov, private communication modified in order to describe the new data [5] N. Lo. Iudice et al., Phys. Rec. C 77, while simultaneously keeping the 044310 (2008) satisfactory description of the Ce, Ba, and Xe isotones [5]. C. Bauer A more detailed analysis is ongoing and especially the extraction of the B(E2) value IS492: Recent results from of the contaminant 140Sm seems to be an radiotracer PL at ISOLDE exciting possibility. Photoluminescence (PL) spectroscopy is one of the most commonly used techniques in References: the characterization of semiconductors, [1] N. Pietralla et al., INTC P-268 (2009) enabling high resolution study of even low [2] G. Rainovski et al., Phys. Rev. Lett. 96,

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concentrations of defects in the material donor impurities, and the range of beams relatively easily. However, one of the main available at ISOLDE allowed implantations limitations of the technique is its chemical of Zn, Ga, In, Cd, Ag and As to be carried blindness, and so identifying the origin of out to investigate the behaviour of donor features can take many years – even impurities in ZnO. These experiments have decades. The combination of PL with provided the first chemical identification radioactive isotopes offers the possibility to that Ga and In are responsible for at least gain that otherwise-lacking chemical four of the ten main optical features dimension. Furthermore, by combining commonly seen in this material. techniques such as uniaxial stress and Furthermore, luminescence has been Zeeman spectroscopy with PL we are able observed for Ge impurities for the first time, to gain structural and electronic information and recent work has focused on the about the centres, allowing a very complete performing Zeeman and stress experiments description and understanding of PL on Ge-centres and also on isoelectronic systems. impurities such as Hg and Cd. PL has been carried out at ISOLDE since the mid-1990s, and now includes an on-site off- Recent publications involving ZnO line laboratory for the study of the effects of i. Karl Johnston, Joseph Cullen, Martin relatively short-lived isotopes. Recent focus Henry, Enda McGlynn and Monica Stachura has been on identifying impurities in ZnO “Evidence for As lattice location and Ge and on unraveling what were thought to be bound exciton luminescence in ZnO well-understood systems in Si. implanted with 73As and 73Ga” Physical (a) Donor-related impurities in ZnO Review B 83 125205 (2011). After a burst of activity in the 1960s, the ii. J. Cullen, K. Johnston, M. O. Henry, study of ZnO remained something of a E. McGlynn and the ISOLDE Collaboration niche area until the early 2000s when “Photoluminescence due to group IV predictions such as room temperature impurities in ZnO” Accepted for publication ferromagnetism and the demand for in MRS proceedings” (2012) blue/UV laser emissions drove researchers to “re-discover” this material once again. However, in spite of considerable effort, many of the fundamental properties of the material remained unclear: although well- known to be an n-type semiconductor many of the impurities giving rise to this behaviour remained unidentified. Work carried out at ISOLDE has helped to identify a number of the donor defects responsible for this behaviour and has also opened up some new avenues of research exploring the roles of double donors and isoelectronic impurities in the material. Figure one shows a snapshot from the Figure 1: Elements to the right of Zn will periodic table in and around Zn. The group act as donors in ZnO, if occupying a Zn site. III elements Al, Ga and In – when Experiments at ISODLE have allowed the occupying a Zn site in ZnO – become single chemical identification of PL features

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associated with Ga, In and Ge in ZnO for the first time. These individual features can be understood in terms of the number of atoms involved in (b)Metal impurities in mono-isotopic Si the centre and further study into this area Silicon is still far and away the pre-eminent produced more surprises; it turns out that semiconductor and lays strong claims to be many of the previously studied centres the most studied material in the world. Its which were thought to originate from extensive use in the electronics industry and isolated or pairs of transition metals actually increasing deployment as the basis for solar turn out to be multi-atom centres e.g. four cells demands a detailed understanding of Cu atoms. The Cu4 centre can be thought of the role of defects in this material. as a base, and this can then in turn be However, although a great deal is known “decorated” with other metals such as Ag or about defects and impurities in Si, surprises Li, or with Li or Ag replacing a Cu atom in can still occur. In the past few years very the complex. Determining the numbers of pure essentially mono-isotopic 28Si has atoms in the centres requires at least two been produced – a by-product from the isotopes of the same element, and uniquely, Avogadro project: an initiative to re-define ISOLDE work has combined enriched silicon the kg in terms of Avogadro’s constant. material with radioactive isotopes in the When studied using PL the spectra were case of Au impurities for which there is only quite unlike any others previously seen in one stable isotope. Implantations at ISOLDE Si. In particular, the spectral features were of 197Au – produced from a 197Hg beam, and much sharper than for natural Si due to the decaying into 197Pt) – allowed these studies elimination of inhomogeneous isotope to be furthered and resulted in the broadening. This drastic narrowing of observation of several new Au- and Pt– features can be seen in figure 2(a) where related multi-atom centres involving Cu in the original optical line is shown to consist Si. of a forest of separate lines. There is great excitement in the semiconductor community about these results, and not just in the ‘Ivory Towers’. Centres involving transition metals have a significant effect on device performance, especially on the efficiency of solar cells. The radically different picture of impurities in Si offered by these experiments may allow a greater understanding of impurities

(a) in Si leading ultimately to more efficient and reliable devices.

Recent Publications involving Si

(b) i. M. Steger, A. Yang, T. Sekiguchi, K. Saeedi, M. L. W. Thewalt, M. O. Henry, K. Figure 2 Example of PL spectra obtained Johnston, H. Riemann, N. V. Abrosimov, M. from 28Si. (a) shows the narrowing of F. Churbanov, A. V. Gusev, A. K. optical features which takes place in one Kaliteevskii, O. N. Godisov, P. Becker, H.-J. Cu-related centre. (b) shows spectra Pohl “Photoluminescence of deep defects obtained after implanation at ISOLDE from involving transition metals in Si – new a 197Au beam.

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insights from highly enriched 28Si” Applied separator (GPS). The beam was neutralized Physics Reviews 110 081301 (2011) in a sodium cell. The cadmium atoms were 3 ii. M. Steger, A. Yang, T. Sekiguchi, K. then excited in the transition 5s5p P2 → 3 Saeedi, M. L. W. Thewalt, M. O. Henry,K. 5s6s S1 at a wavelength of 509 nm. Laser Johnston, E. Alves, U. Wahl, H. Riemann, N. excitations in the components of the V. Abrosimov, M. F. Churbanov, A. V. hyperfine structure (hfs) were identified by Gusev, A. K. Kaliteevskii, O. N. Godisov, P. the beam fluorescence as a function of the Becker, and H.-J. Pohl “Isotopic fingerprints Doppler-shifted laser frequency while of Pt containing luminescence centers in scanning the beam velocity. A typical highly enriched 28Si” Physical Review B 81 spectrum of 115Cd is presented in Fig. 1, 235217 (2010) where one can identify the hfs components iii. M. Steger, A. Yang, T. Sekiguchi, K. of the ground state and the isomer. Saeedi, M.L.W. Thewalt, M.O. Henry, K. The measurements determined the ground- Johnston, H. Riemann, N.V. Abrosimov, state spins in the studied range as being M.F. Churbanov, A.V. Gusev, A.D. Bulanov, 1/2, 3/2, and 5/2 in close relation with the I.D. Kaliteevski, O.N. Godisov, P. Becker, corresponding single-particle orbitals of the H.-J. Pohl “Isotopic fingerprints of gold- sdgh shell. Evidence is found whether the containing luminescence centers in 28Si” isomeric configuration is 11/2- in all odd Physica B 404 5050 (2009) cases. The data is sensitive to the changes in the degree of collectivity between the K. Johnston, M. Henry ground states and the isomers, not only from their quadrupole moments, but also through their rms charge radii. This has the IS497: Ground States and potential to solve the question if the Isomers of Cadmium by High- cadmium isotopes are spherical vibrators or Resolution Laser Spectroscopy weekly deformed rotors.

The isotopic chain of cadmium was studied by high-resolution laser spectroscopy for the first time. The goal was to determine nuclear spins, electromagnetic moments and root mean square (rms) charge radii of ground and isomeric states along the isotopic chain, ultimately reaching the neutron 50 and 82 shell closures. In 2011 the intense beams of 106-124,126Cd were studied by fluorescence spectroscopy, which also covered the isomers in the odd 111-123Cd. The measurements were carried 115 out with the collinear laser spectroscopy Figure 4 Hyperfine structure of Cd (red) 115 m setup at ISOLDE-CERN. High-energy and Cd (blue). protons impinging on a uranium carbide It is planned to extend the measurements target produced neutron-rich cadmium towards the neutron 50 and 82 shell isotopes, which were laser ionized, closures in 2012 to address isotopes of accelerated to energy of 50keV and mass specific interest in these regions. In order to separated with the general purpose improve the sensitivity to the very exotic

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species at both ends of the shell, the between ISOLDE experiments with 57Mn measurements will be carried out using and home laboratory studies using 57Fe. bunched beams from ISCOOL. Furthermore, Some of the spectra obtained are shown in 2 2 the 5s S1/2 → 5p P3/2 transition at 215 nm Fig. 1. in the cadmium ion will be used. Offline tests have shown the feasibility of the θ = 0° experiment. θ = 40° D.T. Yordanov for the COLLAPS Collaboration Fe θ = 62° D IS501:Lattice locations and Emission (a.u.) Fe C θ = 80° properties of Fe in Co/Fe co- implanted ZnO -4 -3 -2 -1 0 1 2 3 4 Velocity (mm/s) Magnetic semiconductors obtained by dilute Fig. 1: 57Fe emission Mössbauer spectra doping with 3d-metal impurities have been obtained of an Fe/Co implanted sample at of major interest in recent years due to the room temperature under the emission potential applications in spintronics. For angles relative to the crystal symmetry axis ZnO, room-temperature ferromagnetism as indicated (from [3]). was predicted by theory [1], but grossly inconsistent experimental results have been One conclusion is evident from the spectra obtained. in Fig. 1; the spectra clearly depend on the 57 At ISOLDE, our group, utilizing Fe emission angle. This shows that some of emission Mössbauer spectroscopy following the probe atoms are in an environment 57 implantation of the parent Mn (T½ = 1.5 where they can “see” the lattice structure, min.), has been investigating the role of Fe or in crystalline sites (FeC). Another part of in ZnO. Our results have shown that in the the probe atoms are in an environment, not 13 57 2 dilute regime (<10 Mn/cm ), the Fe is showing any angular dependence (FeD), 2+ 3+ found as Fe and Fe in paramagnetic most likely in a damage environment, where sites, and spectra shows the absence of any information on the local lattice structure is spin interactions with defects created in the lost. Both fractions are due to Fe2+. implantation process [2] i.e. suggesting that Although the splitting of the two lines of the dilute Fe impurities cannot be the source of crystalline component (FeC) is higher than is magnetism observed by some authors. observed for Fe2+ substituting Zn2+ in ZnO, Moreover, Mössbauer spectra obtained from the electron density is exactly the same, conversion electron Mössbauer and the increased splitting is probably due spectroscopy (CEMS) on samples implanted to small distortions of the lattice. The 15 57 2 with >10 Fe/cm are very different from spectra obtained by us are practically 57 those obtained by us using Mn. To identical to spectra obtained by CEMS on elucidate this apparent dilemma, a sample 57Fe implanted samples. However, angular 57 12 -2 was implanted with Co ~ 5×10 cm with dependence was not considered in those 57 14 2 an impurity level of Fe of ~5×10 cm- . measurements. Although for most cases an unacceptable From low temperature measurements [3], it level of contamination, this was beneficial was observed that the relative spectral for the current study, bridging the gap fraction of the damage fraction component

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(FeD) became much higher than that of the IS504: Probing the semi- crystalline fraction (FeC). This is well known magicity of 68Ni via the 3H(66Ni, from Mössbauer spectroscopy, if the Debye- 68Ni)p two-neutron transfer Waller factor of the fraction that increases relatively in intensity at lower temperatures reaction in inverse kinematics is much lower than that of the crystalline 68 site. This is characteristic for an interstitial The region around the nucleus Ni, with a type of defect, where there is less binding shell closure at Z = 28 and a sub-shell closure at N = 40, has drawn considerable to the lattice. 68 Upon annealing at T > 400ºC part of the interest over the past decades. Ni has properties that are typical for a doubly- damage iron component(FeD) was found to 3+ magic nucleus, such as a high excitation be relocated into Fe species showing fast + + spin relaxation. The most likely cause of this energy and low B(E2:2 -0 ) transition probability for the first excited 2+ level [1-3] spin relaxation is spin-spin relaxation + between close (<5 Å) Fe3+ pairs: evidence and a 0 level as the first excited state [4]. However, recently it has been suggested of the first stages of precipitation. Such 68 precipitates would easily give a signal in that the magic properties of Ni arise due magnetic measurements and these findings to the fact that the N = 40 separates the show a possible pathway for the formation negative parity pf shell from the positive of such precipitates [3]. parity 1g9/2 orbital [5,6], and indeed, recent References: mass measurements [7,8] have not [1] T. Dietl, H. Ohno, F. Matsukura, J. revealed a clear N = 40 shell gap. Despite Cibert, and D. Ferrand, Zener Model all additional information that was acquired Description of Ferromagnetism in Zinc- over the last decade the specific role of the N = 40 is not yet understood and a new Blende Magnetic Semiconductors, Science 68 287 (2000) 1019 experimental approach to study Ni was [2] H. P. Gunnlaugsson, T. E. Mølholt, R. proposed. Namely, a two neutron transfer (t,p)-reaction on 66Ni to populate amongst Mantovan, H. Masenda, D. Naidoo, W. B. + Dlamini, R. Sielemann, K. Bharuth-Ram, G. others the 0 ground state and characterize the 0+ and 2+ excited states in 68Ni. The Weyer, K. Johnston, G. Langouche S. + 68 Ólafsson, H. P. Gíslason, Y. Kobayashi, Y. nature of low lying 0 states in Ni have Yoshida, M. Fanciulli and the ISOLDE recently been discussed in [9]. Collaboration, Paramagnetism in Mn/Fe The experiment was successfully performed in September 2011. A 66Ni beam with an implanted ZnO, Appl. Phys. Lett. 97 (2010) 6 142501, doi:10.1063/1.3490708 average intensity of 4.2 x 10 pps was [3] H. P. Gunnlaugsson, K. Johnston, T. E. accelerated to an energy of 2.6 MeV/u using Mølholt, G. Weyer, R. Mantovan, H. REX and directed onto a tritium loaded Masenda, D. Naidoo, S. Ólafsson, K. titanium target in the T-REX particle Bharuth-Ram, H. P. Gíslason, G. Langouche, detection array [10]. γ rays were detected M. B. Madsen and the ISOLDE using MINIBALL. The beam energy was Collaboration, Lattice locations and reduced to avoid fusion with titanium in the properties of Fe in Co/Fe co-implanted ZnO, target. The target ladder was put at a high Appl. Phys. Lett. 100 (2012) 042109, doi: voltage (+2000V) to avoid that electrons 10.1063/1.3679692 would reach the silicon detectors of the CD H. Gunnlaugsson for the Mössbauer and Barrel in T-REX. collaboration at ISOLDE/CERN

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[2] O. Sorlin et al., Phys. Rev. Lett. 88, 092501 (2002). [3] N. Bree et al., Phys. Rev. C 78, 047301 (2008). [4] M. Bernas et al., Phys. Lett. B 113, 279 (1982). [5] H. Grawe and M. Lewitowicz, Nucl. Phys. A 693, 116 (2001). [6] K. Langanke et al., Phys. Rev. C 67, 044314 (2003). [7] S. Rahaman et al., Eur. Phys. J. A 34, 5 Figure 1: Doppler-corrected gamma rays in (2007). coincidence with protons. The black [8] C. Guénaut et al., Phys. Rev. C 75, spectrum shows prompt coincidences and 044303 (2007). the red random coincidences. [9] D. Pauwels et al., Phys. Rev. C 82, 027304 (2010). [10] V. Bildstein et al., Prog. Part. Nucl. Phys. 59, 386 (2007).

J. Elseviers on behalf of the IS504 collaboration

IS518: New mass values of neutron-rich Fr and Ra from Figure 2: Proton energy versus laboratory ISOLTRAP scattering angle. Transfer to the ground state is clearly present. The masses of very neutron-rich francium and radium isotopes, 224,226,228-233Fr and A first analysis of the data at IKS, KULeuven 233,234Ra, have been determined at indicates the population of several states in 68 ISOLTRAP [1] in 2011. The results include Ni. Figure 1 shows the Doppler-corrected γ 228,231-233 233,234 six masses: Fr and Ra, which rays that were observed with MINIBALL in have been measured for the first time. The coincidence with protons. The black other mass values have been improved. spectrum shows prompt coincidences and The ISOLTRAP measurement cycle starts the red spectrum the random coincidences. with accumulation, cooling and bunching of The preliminary analysis shows a surprising the ISOLDE beam in a radio-frequency result, namely, except for the ground state, quadrupole (RFQ) buncher. From there, the which has a strong population (see Figure ions are transferred to the recently 2), we do not see clear evidence for the implemented electrostatic ion-beam trap population of other 0+ states through the (MR-ToF-MS [2,3]; see also ISOLDE- two-neutron transfer. newsletter 04/2011). Together with a fast- References: switching beam-gate it serves as a multi- [1] R. Broda et al., Phys. Rev. Lett. 74, 868 reflection time-of-flight mass separator. In a (1995). second purification step, the ions of interest

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are exposed to a mass-selective buffer-gas cooling technique in a preparation Penning trap. Finally, the actual mass measurements are performed in the precision Penning trap. The ISOLTRAP setup is sketched in Fig. 1. Although nuclei around magic numbers have been subject to extensive studies, not much data exists for the evolution of the N=126 shell. The new data provide two- neutron separation energies S2n up to N=146 thus offering information about structural changes even towards the next shell closure at N=168. Furthermore, they Figure 2: Two-neutron separation energies serve as valuable input for the development of Ra, Fr, and Rn isotopes including the new of nuclear structure models in this very values based on the recent ISOLTRAP heavy, neutron-rich mass region. In measurements. addition, these masses lie in a region particularly interesting for nucleosynthesis References: [4] since the rapid neutron-capture process [1] M. Mukherjee et al., Eur. Phys. J. A 35 (r-process) can recycle due to the process (2008) 1. of fission. Together with the Rn data from [2] R. N. Wolf et al., Hyperfine Interact. 199 2008 [5], the Fr and Ra masses provide (2011) 115. beta-decay energies for the evaluation of [3] R. N. Wolf et al., Int. J. Mass Spectrom. beta-decay half-lives that greatly influence 313 (2012) 8. the r-process. Thus, the new mass values [4] D. Lunney et al., Rev. Mod. Phys. 75 can help to consolidate the nucleosynthesis (2003) 1021. path for the r-process. [5] D. Neidherr et al., Phys. Rev. Lett. 102, 112501 (2009)

M. Rosenbusch for the ISOLTRAP collaboration

Figure 1: Sketch of the ISOLTRAP mass spectrometer with its linear Paul trap, electrostatic ion-beam trap, and two Penning traps. Upper left: time-of-flight resonance of the recently measured 233Fr.

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Target and Ion Source Development:

The program on target and ion source development resulted last year in different beam improvements and new technologies used for the first time in an “online” configuration. This combines online operation of ion sources, such as a cold Figure 2: Helicon source seen from the plasma Helicon ion source, a bulk Rhenium beam extraction side, with the visible first surface ion source and a VADIS ion source extraction stage. mounted on a molten lead target unit, a RF- driven LIST trap combined with RILIS for This project is now taken over by Dr the purification of beams, new types of Matthias Kronberger, previously active in H- targets such as calcium oxide nanomaterials ion source development for the injector displaying improved release properties, and upgrades under construction at CERN, last but not least, a molten fluoride salt hoping we can find an additional margin for target under development for neutrino efficiency improvements. Another milestone physics. Figure 1 provides an overview of was the successful operation of the LIST these different results. technology, jointly developed within a

collaboration of the TISD, the RILIS and Mainz university teams [2]. When combined with a Titanium foil target, suppression factors of isobaric impurities of more than 3 orders of magnitude could be achieved, whereas RILIS Mg ions could be delivered with some x30 yield drop on average. After

these successful online tests, further Figure 1: Highlights on delivered developments are taking place together beams and developments which took place with a foreseen first unit to deliver beam to in 2011 at ISOLDE. physics experiments this year. These different developments were completed Following up on the report given in with the confirmation that a VADIS ion the previous Newsletter, year 2011 source is suitable to produce intense and witnessed first in-beam tests of a Helicon- pure mercury beams from a molten lead type cold plasma ion source developed by target, leading to a fivefold improvement on Pekka Suominen for the production of intensities versus the ones obtained with molecular neutron-rich carbon beams [1]. historical MK3 FEBIAD ion sources, Figure 3. With IS445, stable operation and delivery of Full compatibility of the VADIS molybdenum 16,17C as CO+ ions could be monitored, with cavity with metal vapors and no pollution of yet too low intensities to fulfill their physics the extraction electrode could be confirmed. objectives. The two stage extraction Finally amongst the developments that took electrode configuration provided adequate place on the ion source technologies, a bulk online beam profiles, Figure 2. rhenium cavity was designed and manufactured to replace the more

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traditional surface ion sources made of 19/20, equivalent to the highest honors for tungsten, tantalum or niobium. With its high such a diploma at the University of Aveiro work function of ca 5eV, improvements on [3]. ionization efficiencies, hence of 30Na beam intensities, were witnessed, and will also hopefully serve for some future requests on alkali and earth-alkali elements.

Figure 4: CaO nanostructure identified by TEM microscopy

References: Figure 3: Comparison of yields of mercury beams from molten lead targets. [1] P. Suominen, P. Sortais, T. Stora, O.

Tarvainen, Plasma Ion Sources for 1+

molecular radioactive ion beams, ARIS On the front of target material 2011, Leuven, developments, highlights were obtained last https://iks32.fys.kuleuven.be/indico/contrib year by the extension of the ISOLDE utionDisplay.py?contribId=194&confId=0, nanomaterials portfolio with a third member accessed Feb 2012. in the family, calcium oxide joining up the [2] F. Schwellnus et al., Rev. Sci. Instrum. available silicium carbide and yttrium oxide 81, 02A515 (2010). materials, Figure 4. This result, which [3] J. P. Ramos, Effect of Calcium Oxide already provided the WITCH experiment Microstructure on the Diffusion of Isotopes, with high yields of 35Ar beams, is even more CERN-THESIS-2012-008, interesting for more exotic beams, for which http://cdsweb.cern.ch/record/1425438?ln=e reduced diffusion times that originate from n the nanostructure translates into increased yields. The conservative operation A. Gottberg, T. Stora temperatures and proton pulse intensities allowed us to provide beams with constant intensity over several days, quite on the contrary to what was observed with previous CaO targets operated at ISOLDE at higher temperatures and higher proton pulse intensities. This work was the subject of a master thesis in material sciences by Joao Pedro Ramos, for which he obtained

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The Dual RILIS: the increasing demand for RILIS beams. This complementary laser setup enables the use of the many already established RILIS ionization schemes that require wavelengths Through the use of highly selective and produced by Ti:Sa lasers. Additionally, since efficient stepwise resonant ionization the two systems can be used either schemes, the ISOLDE RILIS has so far been independently or in combination with each applied for ionizing 28 of the elements other, the flexibility for switching from one produced at ISOLDE. The unique element ionization scheme to another is greatly selectivity of the laser ion source improved. The main benefits are: complements the mass selection process of • Reduced switching time from one the ISOLDE separator magnets to provide element to another high purity ion beams of the chosen • Increased range of accessible isotope. RILIS operation is requested by the elements users for over 2000 hours per year, • Higher ionization efficiency due to amounting to over 50% of the total ISOLDE increase in laser power (dye + Ti:Sa) beam-time. and wider tuning range

• The solid-state nature of the Ti:Sa The RILIS dye laser system reduces maintenance work (no dye The RILIS comprises three dye lasers that can be focused and overlapped at a change) distance of ~20 m into the ionizer tube at The RILIS Ti:Sa system comprises two the ISOLDE target. Up to three days of commercial 60 W frequency doubled preparation are needed for a change from Nd:YAG pump lasers and three broadly one element to another, this includes tunable solid-state Ti:Sa lasers. The laser replacement of the dye solution (more than parameters (10 kHz repetition rate, 5 W ten different organic dyes are used), laser maximum output power and spectral line set-up and alignment of the beams into the width of ~5 GHz) are well adapted to the source. The RILIS dye laser system has RILIS requirements. The basic cavity design been significantly improved since its first was adopted from the University of Mainz. demonstration of selective ionization of The Ti:Sa laser setup was developed further radioactive Yb isotopes in 1992 [1]. In by the RILIS team for improved operation in recent years the system has been on-line conditions where time for setup and progressively upgraded: The copper vapor alignment is limited [3]. pump laser was replaced by commercial For the implementation of the new laser solid-state diode pumped Nd:YAG lasers in system without jeopardizing a successful 2009 and the home-built dye lasers were restart of the RILIS dye laser system, the exchanged with state of the art commercial limited space inside the RILIS cabin was the versions in 2010. [2] biggest challenge. The layout of the RILIS was rearranged during the shut-down A Complementary Laser system period 2010/11. Two additional optical During 2011 a second independent laser tables and the obligatory laser safety system based on Nd:YAG pumped tunable screening were installed. A schematic view titanium:sapphire (Ti:Sa) lasers was is shown in Fig.1. installed alongside the RILIS dye laser system. It offers great potential in meeting

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down-time for users, whilst maintaining the same efficiency. In-source spectroscopy Having a second laser system in place allowed for opportunistic use of ISOLDE beamtime. The Ti:Sa system was used for in-source spectroscopy using a Faraday cup to detect ions. Such micro-beamtimes were scheduled mainly during REX setup when

the central beam line was in use and no Fig 1. Schematic view of the upgraded other user could take beam from an RILIS laser setup. operational target. This spectroscopy work resulted in the first experimental and New modes of operation - The Dual precise measurement of the ionization RILIS potential of the astatine atom (article in In 2011 RILIS was used on-line for a record preparation). The newly available efficient time of 2757 h (184 h for TISD), producing ionization scheme for astatine enables ion beams of 16 different elements. For further in-source laser spectroscopy work to comparison, in 2010 the RILIS ON time investigate the isotope shifts and hyperfine amounted 2096 h. New modes of RILIS splittings as well as the continuation of the operation were investigated and some were successful experiments for beta-delayed already successfully used to provide beams fission [4] for the astatine isotopes. to ISOLDE users. In the ‘Ti:Sa only’ mode up to 50 W of the Nd:YAG dye pump laser References: is available for non-resonant ionization [1] V.I. Mishin et al., Nucl. Instrum. and providing highest efficiencies (tested for Pr, Meth. Phys. Research B 73, 550 (1993) Tl and Yb). For the ‘mixed mode’ both laser [2] V.N. Fedosseev et al., Rev. Sci. Instrum. systems (dye and Ti:Sa) are synchronized 83, 02A903 (2012). and work together. The laser type is chosen [3] S. Rothe et al., in J. Phys. Conf. Ser., depending on the highest efficiency in the Vol. 312 (IOP Publishing, 2011) p. 052020. required wavelength range (demonstrated [4] A. Andreyev et al., Phys. Rev. Lett. 105, for Ag and At). In ‘backup mode’ both 1 (2010). systems could provide the same wavelength. In the case for Ni the Ti:Sa S. Rothe, V. Fedosseev, B. Marsh system was used to produce the final ionization step resulting in twice the ionization efficiency of the ‘dye only’ setup. In the case for Zn the first step wavelength was obtained by both laser systems simultaneously i.e. four beams of three different wavelengths were transmitted to the ionizer tube. This enabled 3rd and 4th harmonics generation under reliable conditions, reducing damage to the nonlinear crystals and thus minimizing

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TSR at HIE-ISOLDE Project:

TSR@HIE-ISOLDE Collaboration

In 2011, after a positive evaluation of the Letter of Intent for installing a storage ring facility TSR at HIE-ISOLDE [1], our collaboration (see Ref. [2]) has prepared a full-scale Technical Design Report which has been submitted to the INTC in January 2012 [2]. If approved, we will build the first storage ring coupled to an ISOL-type radioactive beam facility. Such a facility will provide a capability for experiments with stored secondary beams that is unique in the world. The envisaged physics programme is rich and varied, spanning Figure 1. A possible location of the TSR from investigations of nuclear ground-state storage ring at the HIE-ISOLDE. properties and reaction studies of astrophysical relevance, to investigations The operation of the TSR at Max-Planck with highly-charged ions and pure isomeric Institute for Nuclear Physics in Heidelberg beams. In addition to experiments will be stopped in the end of 2012. It is performed using beams recirculating within expected, that once the new building is the ring, cooled beams can also be available, the transport, reassembly and extracted and exploited by external commissioning of the ring at ISOLDE can spectrometers for high-precision be accomplished within about 15 months. measurements. A detailed description of the In order to pursue the physics goals aimed proposed physics cases can be found in at within the TSR@HIE-ISOLDE Project, Refs. [1,2]. several R&D studies have to be done. Several options have been considered for Therefore, a number of dedicated working the installation of TSR at ISOLDE. The groups have been formed. The TSR@HIE- scenario which was found to be the optimal ISOLDE is an open collaboration which is the installation of the ring in a new invites all interested researchers to help us building located at the back (west side) of exploring the extremely rich scientific the ISOLDE experimental hall (see Figure). potential of the envisaged TSR@HIE- The floor of the new building would ISOLDE facility. approximately be 2.8 m above the floor of the existing hall due to an essential [1] A. Andreyev et al., Letter of Intent, infrastructure tunnel preventing the ring to CERN-INTC-2011-019 / INTC-I-133 (2011). be at equal height of the transfer beam line. [2] M. Aliotta et al., Proposal, CERN-INTC- To deliver the beams from the HIE-ISOLDE 2012-027 / INTC-O-014 (2012). to the TSR a tilted beam line will have to be designed. The planned building will allow for Y. Litvinov for the TSR at HIE-ISOLDE installation of external setups which would Collaboration profit from slowly-extracted electron-cooled beams.

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How to obtain access to (CERN Electronic Document Handling) well in advance of your arrival at CERN6. the ISOLDE hall 5. Obtain a radiation dosimeter at the Dosimetry service, located in Building 1. Register at the CERN Users office1. You 557. Two options exist: need to bring a. Temporary dosimeter. Issued only a. Registration form signed by your once per calendar year for a team leader or deputy2 maximum of 2 months. 3 b. Proof of attachment to Institute or b. Permanent dosimeter. A medical University in English or French certificate8, valid for 24 months, is c. Passport required. The permanent dosimeter d. Copy of medical insurance (for needs to be readout monthly9. illness, private accidents, and work 6. Apply for access to ISOLDE hall using accidents and disability arising from EDH: such accidents at CERN) https://edh.cern.ch/Document/ACRQ. 2. Get your CERN access card in Building This can be done by any member of 55 your collaboration (typically the contact With this registration procedure you person) having an EDH account10. become a CERN user4. 3. Follow the CERN basic safety course Find more details at the information about (levels 1 to 3): registration for Users page. a. If you have a CERN account, you can access the Safety Awareness course New users are also requested to visit the on-line at the web page ISOLDE User Support office while at CERN. http://sir.cern.ch, from your Opening hours: computer, inside or outside CERN. Mon., Tues., Thurs., Fri. 08:30-12:30 b. If you have not activated your CERN Mon. & Thurs. 13:30-15:30 account, there are some computers available for use without the need to You can also use the summary “Registration log in on the first floor of building 55 and ISOLDE access” flow-chart as guidance. (Your CERN badge will be needed in order to prove your identity). 4. Follow the radiation protection course only if you need to get a permanent personal dosimeter5. Please make a reservation for the course via EDH

1 http://cern.ch/ph-dep-UsersOffice (Building 61, open 6 8:30-12:30 and 14:00-16:00, closed Wednesday morning). If it is not possible to sign up for a course, a temporary 2 Make sure that the registration form is signed by your dosimeter can be issued for the first registration at CERN. team leader before coming to CERN or that it can be 7 http://cern.ch/service-rp-dosimetry (open only in the signed by the team leader or deputy upon arrival. mornings 08:30 - 12:00). 3 Proof of attachment to Institute or University should not 8 The medical certificate must be brought in person to the be signed by the person nominated as your team leader. Dosimetry Service (either by the user or a representative) 4 The first registration as USER needs to be done 9 There are reader stations at the ISOLDE hall and the personally, so please note the opening hours. If needed CERN main building. You can leave your permanent the extension of the registration can be delegated or dosimeter in the rack outside the ISOLDE User Support performed on-line via EDH. office. 5 The radiation protection course is mandatory to obtain a 10 Eventually you can contact Jenny or the Physics permanent personal dosimeter. coordinator.

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Contact information

ISOLDE User Support Jenny Weterings [email protected] +41 22 767 5828

Chair of the ISCC Maria Jose Gª Borge [email protected] +34 91 59 01 614

Chair of the INTC Peter Butler [email protected] +44 151 794 3443

ISOLDE Physics Section Leader Yorick Blumenfeld [email protected] +41 22 767 5825

ISOLDE Physics Coordinator Magdalena Kowalska [email protected] +41 22 767 3809

ISOLDE Technical Coordinator Richard Catherall [email protected] +41 22 767 1741

HIE-ISOLDE Project Leader Yacine Kadi [email protected] +41 22 767 9569

More contact information at https://isolde.web.cern.ch/ISOLDE/default2.php ?index=index/groupindex.htm&main=group/con tacts.php and at https://isolde.web.cern.ch/ISOLDE/default2.php ?index=index/groupindex.htm&main=group/pla ces.php

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