Gas cell-based laser ion sources: Production and study of exotic nuclei
Iain Moore JYFL, Finland Outline of talk
General introduction to RIB production
Practicalities of ion survival in gas
In-gas cell laser resonance ionization
Gas jet laser ionization
Case examples and outlook
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 The nuclear physicists playground
Our boundaries • ~7000 bound nuclei between 2
J. Erler et al., Nature 486 (2012) 509 Our questions • Nuclear structure • Nuclear astrophysics • Fundamental physics • Applications
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 New discoveries with new techniques
Radioactivity discovered Reactors: n on U First ISOL experiments
Selective detection : decay Light-ion induced spallation Heavy-ion induced fusion Projectile + target fragmentation; In-flight separation <1940 1940 1950 1960 1970 1980 495 822 1244 1515 2010 2270 M. Huyse
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 The ISOL Radioactiveatoms primary beam primary Mass Mass selection High Low ion beam ion - - energy energy
method
I.D. Moore, Advanced
of RIB First TRIUMF (Canada), GANIL TRIUMF (Canada), (France), ALTO elements High
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and production on on Laser Applications ,
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The in-flight method of RIB production
First in-flight separator, Oak Ridge (1958)
High-energy
primary beam
Projectile fragments
Isotope selection
Medium-energy • Very fast separation: μs half-lives ion beam • Beams of ALL elements. • Often poor beam quality. • Precision experiments not directly accessible. GANIL (France), GSI (Germany), NSCL/MSU (USA), RIBF RIKEN (Japan), (FRIB, FAIR)
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 The ion guide / gas catcher method …an ISOL system for ALL elements, fast extraction
Projectile source ``The best of both worlds´´ Fast beams Purification in-flight
Thin target
Ion survival Neutralization
mass separator Electrical fields
Ion guide Laser re-ionization
technique Z selectivity
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 What do we mean: nuclear reaction? What do we mean by a nuclear reaction? • Handout 1
Task 1: create a source of 56Co and calculate the rate of productionI.D. Moore, Advanced S chool on Laser Applications at Accelerators, Sept. – Oct. 2014 Outline of talk
General introduction to RIB production
Practicalities of ion survival in gas
In-gas cell laser resonance ionization
Gas jet laser ionization
Case examples and outlook
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Complexity of gas cell processes
• High density gases to stop energetic particles • High IP of noble gas atoms prevents charge exchange between ions and buffer gas atoms
He or Ar Photo ionization few 100 mbar Diffusion losses Metastable state primary/secondary beam e- e- - + e + + e- e- + - + + e e- e- * + + + - e- - e + + e e- + e- + β - - + e e- e- e- e Stopping Molecular formation: Decay Neutralization atoms and ions losses - 3 body
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Molecular ion formation X+ + M → XM+ dn/dt = -kn[M] Towards mass t = 1/k[M] separator
Reaction Rate constant SPIG k (cm3s-1) Exit hole + -11 Mo + O2 7.5×10 + -13 Ru + O2 1.7×10 + -14 Rh + O2 9.2×10 + -11 Ti + H20 6.1×10 Ti+ + O 4.6×10-10 Ar 500mbar Ar/He from 2 gas + -10 Y + O2 4.1×10 purifier + -10 Th + O2 6.0×10 Filament + -10 U + O2 8.5×10 (yttrium) + -10 Zr + O2 5.0×10 + -13 Ag + O2 1.0×10 Laser beams
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Effect of impurity levels in the gas
Y+ 18 + YO+ 350 Y YO+(H O) 2 + + ) 15 YO (H O) 300 YO
-1 2 2 YO+(H O) 2 3 12 YO+(H O) 250
2 4 1000 1000 s ( 200
9 150 6
Counts / bin / Counts 100 Count rate 3 50 0 0 3500 3600 3700 3800 3900 4000 0 500 1000 1500 2000 Time (ms) Time (ms) Laser on t = 5.1(4) ms t = 96(10) ms Question: What impurity levels do these timescales correspond to? T. Kessler, I.D. Moore et al., NIMB 266 (2008) 681
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Lets add some beam from our cyclotron
Towards mass separator • Ionization processes • Recombination processes SPIG • Space charge effects Target (~ mg/cm2) Exit hole
Cyclotron beam
Ar 500mbar Ar/He from gas purifier Filament
Laser beams
• Effective volume for laser ionization <1% of the ion guide volume • Laser ionization must be applied in a C (l/s) = 0.45·d(mm)2 He t = V/C region of low ion-electron density 2 evac CAr(l/s) = 0.14·d(mm) How can we suppress this ”plasma”? I.D. Moore et al., NIMB 268 (2010) 657
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Separate the plasma and ionization chambers
Laser beams Ar/He Longitudinal from gas Separation of stopping and laser purifier ionization volume improves: • Laser ionization efficiency at high cyclotron beam current Beam from Cyclotron • Increasing selectivity (collection of non-neutral ions) Target
Ionization chamber Ion Collector 58Ni(p,n)58Cu
(τ½=3.2s) Eff. ~1% Exit hole Ø 0.5 – 1 mm SPIG Yu. Kudryavtsev et al., NIM B 267 (2009) 2908 M. Reponen, I.D. Moore et al., NIMB 317 (2013) 422
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Outline of talk
General introduction to RIB production
Practicalities of ion survival in gas
In-gas cell laser resonance ionization
Gas jet laser ionization
Case examples and outlook
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Just in case you forgot……
non-resonant excitation of ionization of ionization auto-ionizing states Rydberg-states extraction IP ~6 eV (5-9 eV) field or
-17 2 -15 2 collisional sI ~10 cm sI ~10 cm higher excited ionization
states
first excited E1
state energy At -12 2 sR ~10 cm
ground state E0 0 eV
SELECTIVITY & EFFICIENCY B. Marsh; K. Wendt
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 The nuclear fingerprint on the atomic structure
+ 20 μeV Y Model Dependent Model Independent (inferred) (measured) d 2 Dynamic / Sizes Isotope shift
Qs
Hyperfine Splitting Single / few Spins particle configurations
μ RICH NEUTRON MORE STABLE
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Workhorse: Collinear fast beam laser spectroscopy Applied Doppler tuning voltage CW tunable laser beam (~1mW, few MHz)
30-60kV
Doppler broadened profile
n n0
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 In-source RIS vs. collinear spectroscopy
IN-SOURCE (RIS) COLLINEAR • Selective process • High resolution • Short lifetimes, low yields (<1 ion/s) • Scanning voltage, not frequency • High detection efficiency • Detect photons • Poor resolution (100-1000× < CLS) • Beams of some 103 ions/s
- 800 6 6- 722 6- 700 + 68 1+ 0 1 Cu 600 68 500 Cu 400 +
1 (g.s.) Counts 300
200
100
0 10000 15000 20000 25000 I. Stefanescu et al., PRL 98 (2007) 122701 P. VingerhoetsRelative et Frequencyal., PRC 82 (2010) (MHz) 064311
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Broadening of atomic transitions (I) Power broadening Natural linewidth: 135 MHz
V. Sonnenschein, I.D. Moore et al., EPJA 48 (2012) 52 • For RIB production we want optimum efficiency 퐼 Γ푝표푤푒푟 = Γ푛푎푡 1 + • For spectroscopy we trade efficiency 퐼푠푎푡 for spectroscopic resolution
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Broadening of atomic transitions (II)
Doppler broadening
• When an atom is in thermal motion we get Doppler broadening. An atomic vapour has a Maxwell-Boltzmann distribution of velocities:
ν0
232 • Hot cavity Th • Crossed beams • Natural linewidth: 35 MHz
• Spectral linewidth: 2.4 GHz (hot cavity) ~170 MHz (crossed beams)
Crossed beams and collinear are basically Doppler-free
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Broadening of atomic transitions (III) Pressure broadening + shift Ar gas Broadening
Ni 11 MHz/mbar 5 MHz/mbar
Shift Cu
-6 MHz/mbar -2 MHz/mbar
T. Sonoda et al., NIMB 267 (2009) 2918
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Limitations of the gas cell approach Laser spectroscopy on Sn isotopes
gbr =32(4) MHz/mbar 1.0 1 0.8 p (mbar) = 100 150 0.6 200 300 400 0.4 500 ref. cell 1.0 0.2 2
0.8 Current on SEM (arb. u.) 0.0 0.6
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0
Wavelength - 39257.05 cm-1 (cm-1) 0.4
• Large pressure broadening 0.2 Current on SEM (arb. u.)
coefficient for λ1 0.0
• Extraction of hyperfine structure 2002 2003 2004 2005 2006 2007 2008 2009 very difficult Wavelength - 59232.69 cm-1 (cm-1)
R. Ferrar et al., NIMB 317 (2013) 570 gsh = 150(10) MHz/mbar
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Outline of talk
General introduction to RIB production
Practicalities of ion survival in gas
In-source laser resonance ionization
Gas jet laser ionization
Case examples and outlook
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Gas jet laser ionization – how and why?
• a quest for PURE radioactive ion beams → (the Laser Ion Source ``Trap´´) B. Marsh
I.D. Moore et al., AIP Conf. Proc. 831 (2006) 511
• an optimal environment for spectroscopy (reduced temperature and pressure)
2 P3/2 Fj 2 P1/2 2 S1/2 Fi F=J+I
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 An “ideal” cold environment for resonance ionization spectroscopy
Temperature vs. Mach number Doppler vs. Mach number
2 2 327.4 nm 4s S1/2 → 4p P1/2 (Cu)
푢 • Mach 12, gas jet T = 6K 푀 = 푎 2 • Doppler FWHM = 200 MHz 훾푘푇0푀 푢 = 훾푘푇 훾 − 1 • Total broadening = 420 MHz a = 푚(1 + 푀2) 푚 2 Yu. Kudryavtsev et al., NIMB 297 (2013) 7
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Free jet laser ionization in Leuven
Bent rf quadrupole design
Towards extraction RFQ
90° bent RFQ Gas cell LASER 1
LASER 2 Shaped rod segments
• Measured HFS of 995(30) MHz agrees with literature: 1013.2(20) MHz
• Doppler shift of 1830(30) MHz; gas jet velocity of 599(10) m/s
Yu. Kudryavtsev et al., NIMB 297 (2013) 7
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Free jet laser ionization at JYFL
0,12
0,09 Ref. cell FWHM = 1.8 GHz 0,06
0,03
0,00 4000 63Cu Gas cell 3000 FWHM = 6.7 GHz 2000 He, 180 mbar 1000
Ion signal (arb. u.) (arb. signal Ion 0 300 Gas jet (LIST) Vjet ~1040 m/s 200 FWHM = 3.9 GHz
100 Laser linewidth dominated 0 -20 -10 0 10 20 I.D. Moore et al., NIMB 317 (2013) 208 n - 915 423.95 (GHz)
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Borrowing ideas from rocket science ! Laval nozzle
15 cm
M. Reponen, I.D. Moore, et al., NIMA 635 (2011) 24
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Development of narrowband pulsed Ti:sapphire laser for gas-jet spectroscopy
Lock-in Amplifier Output (TEM Laselock) HV out pulsed, 30 ns width PSD 3-5 W average power 20 MHz linewidth
Fast piezo Input: mirror CW seed laser 1-100 mW Matisse TS Ti:sa d = n λ cw (100 kHz linewidth)
Fast-switched photodiode amplifier
pump laser Ti:sapphire 10-20 W, 10 kHz crystal
V. Sonnenschein
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Outline of talk
General introduction to RIB production
Practicalities of ion survival in gas
In-source laser resonance ionization
Gas jet laser ionization
Case examples and outlook
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Laser spectroscopy of radioisotopes (2014)
Recent work mostly by At in-source resonance Tl Au ionization spectroscopy
Recent work mostly by Z collinear laser spectroscopy
Key questions What are limits of nuclear existence? Do new forms of nuclear matter exist? Are there new forms of collective motion? Mn Does the ordering of quantum states change? K N P. Campbell, I.D. Moore and M. Pearson, submitted (2014) I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Challenges: moving towards heavy & rare isotopes
212-215Ac
• Radium is the heaviest chain of isotopes studied using optical techiques • Uranium is heaviest ISOL target • Heavier elements are not available • Need fusion reactions in heavy-ion collisions • Low production cross sections • Lack of stable isotopes – lack of optical transitions
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Actinium (Z=89) – choice of scheme is important
continuum 46810.cm-1 46660.6 cm-1 continuum I.P. 43394.45 cm-1 I.P. 43394.45 cm-1 434.7 nm =438 nm 23898.86 cm-1 439.21 nm =418 nm 22801 .1cm-1 4 4P P3/2 transition 5/2 transition
100 215 418.312 nm 438.58400 nm 215 Ac 75 Ac T = 0.17 s
300 1/2
50 2 g.s. D3/2 g.s. 200 2D 3/2 25 100
75 400 214 Ac 214Ac 300 T = 8.2 s 50
1/2
200 Alpha counts in 100 s 100 in counts Alpha 25 100
125 213 75 213 100 Ac Ac T = 0.8 s
75 1/2 50
Alphacounts 100 in s 50 25 25
75 212 75 212Ac Ac T = 0.93 s 50 1/2
50
Alpha counts in 200 s 200 in counts Alpha 25 25
0 0 22801,5 22802,0 22802,5 22803,0 22803,5 22804,0 22804,5 23899,5 23900,0 23900,5 23901,0 23901,5 23902,0 -1 Wavenumbers (cm-1) Wavenumber (cm )
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Study of the rarest element on Earth (Z=85)
Recent interest in At and its IP: • Targeted therapy for cancer treatment • Benchmark for theoretical chemistry of astatine • Benchmark for calculations for IP( 117Uus)
CERN RILIS
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Direct nuclear probing with lasers
Nuclear clock Gamma ray laser Europhys. Lett. 61 (2003) 181 Tkalya, PRL 106 (2011) 162501 PRL 108 (2012) 120802 229mTh 3/2 [631] ΔE ≈ 7.6 eV τ ≈ 25 mins? 5/2 [633] Nuclear Excitation by Qubit: quantum Evolution of Electron Transition computing fundamental constants
PRC 79 (2009) 064303 PRC 79 (2009) 034302 P&T, Izosimov, J. Nucl. Sci. Tech. Europhys. Lett. 61 (2003) 181 Supp. 6 (2008) 1
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 EU Horizon proposal - nuClock Goal • Best optical clocks reach 10-18 precision • nuClock aims to utilize nuclear transition • Consortium: - nuclear physics - atomic physics - quantum optics - metrology - detector- and laser development
3 decades of study; over 70 publications:
• Direct observation of the transition? • Definitive evidence of the existence of the isomer?
→ Collinear or gas cell/gas jet spectroscopy
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Alchemy in the 21st century
Transfermium island Z = 124
Peak of Th, U Z = 126
• Relativistic- and QED- effects gain importance for heavy elements • Fm (Z=100) is heaviest element so far studied with laser spectroscopy Z = 114 • MCDF calculations performed for No (Z=102) and Lr (Z=103) to constrain spectral regions 1 • Search for 7s7p P1 level at GSI, October 2014 S. Cwiok et al, Nucl. Phys. A 611 (1996) 211
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 In-gas Laser Ionization and Spectroscopy NETwork (IGLIS-NET) http://kekrnb.kek.jp/iglis-net/
• KISS (Japan) – towards identification of r process astrophysical site Workshops • In-gas-cell/in-gas-jet spectroscopy at S3, GANIL Leuven (May 2012) - towards N=Z line, heaviest elements • PALIS, RIKEN – parasitic slow beams RIKEN (Dec. 2012) • MARA (JYFL) – nuclei for rp-process JYFL (June 2013)
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Thank you Simulations: hot cavity vs. gas cell
Pressure (mbar) 0 100 200 300 400 500 7 229Th - gas cell 58 6 Ni - gas cell 229Th - hot cavity 58 5 Ni - hot cavity
4
3 FWHM(GHz)
2
1 0 500 1000 1500 2000 2500 Temperature (K)
Laser linewidth 1.8 GHz P. Campbell, I.D. Moore and M. Pearson, submitted (2014)
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 First spectroscopy with the narrowband laser 227 • Tested in Mainz to measure HFS of Ac (τ1/2=22 y) • Same transition applied by LISOL team, May 2014, on 212-215Ac
AI 46347.0 cm-1 IP
424.7 nm
J=5/2 22 801.1 cm-1
438.58 nm J0=3/2 0 cm-1, 6d7s2
• Future: measure 236-244Pu via in-jet RIS followed by high resolution collinear laser spectroscopy (Mainz, Leuven, Manchester and Liverpool) • In-jet RIS in the search for 229mTh (new EU Horizon 2020 application)
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Towards detection of the isomer
Detect via the Hyperfine Structure
Ion trapping of Th3+ Collinear or gas jet spectroscopy
C.J. Campbell et al., PRL 106 (2011) 223001 V. Sonnenschein, I.D. Moore et al., Eur. Phys. J C.J. Campell et al., PRL 108 (2012) 120802 A 48 (2012) 52
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014 Towards the future…
• Continuation of jet studies with laser ionization (nozzles etc) • Spectroscopy of exotic nuclei in the jet with injection-locked lasers
In-gas-cell and in-gas-jet laser ionization at S3 facility, SPIRAL-2, GANIL
I.D. Moore, Advanced School on Laser Applications at Accelerators, Sept. – Oct. 2014