Around the Laboratories

During this time, the Copenhagen in­ sions on staffing were taken, and the stitute, together with the new theory Institute began its work on 1 October DESY group, functioned as an international 1957. Status report centre, attracting eminent scientists Initially, Nordita's interests cov­ from all over the world. ered a broad field of modern physics, During 1982 several major changes The transfer of the CERN theory with special emphasis on nuclear and and improvements were made in group to Geneva in 1955 coincided particle physics and the theory of both the accelerators and the exper­ with a significant effort by Nordic relativity. In 1966, a Finnish proposal imental installations at DESY. The statesmen. It was clear that there to extend Nordita's research into sol­ rebuilt DORIS-II electron-positron was broad agreement for the idea of id state physics found strong sup­ storage ring came into action (see a Nordic Institute for Theoretical port. This has now become one of September issue, page 275) and the Atomic Physics. In November a the main research areas. In more re­ Crystal Ball detector arrived from the meeting in Stockholm gave addition­ cent years there has been a promis­ US (see June issue, page 191). This al strong support to the proposal for ing build-up of activity in astrophy­ detector is now installed in one of a Copenhagen centre, and Finland sics. the two experimental regions of the also added its support. Early the fol­ Nordita functions as a research DORIS-II ring. lowing year, it was agreed that the centre, a meeting place and stimulus In the meantime the second inter­ establishment of Nordita be recom­ for Nordic cooperation in theoretical action region of DORIS-II has been mended to the research councils of physics, and as an educational insti­ occupied by the new ARGUS device the Nordic countries. In the meetings tution providing fellowship opportu­ (see December 1981 issue, page of the Nordic Council's economic nities for younger theoretical physi­ 447). This was moved into the beam committee, the proposal received cists from the Nordic area. Through on 6 September and was able to strong backing, although Norway at its staff and visitor programme, record events just a few weeks first appeared to be hesitant. How­ which is carried out in cooperation later. ever after further discussions, and with the Niels Bohr Institute, Nordita The Crystal Ball detector has al­ after the valuable intervention of plays a part in maintaining contact ready been taking data for some Swedish Prime Minister Tage Erlan- between physicists in the Nordic time. As a first task the upsilon re­ der, the Norwegian Government lent areas and the broader international sonance was remeasured. In one run its support. At a meeting of the Nor­ community. of nine days in August, a few thou­ dic Council in Helsinki in February sand hadronic events were recorded 1 1957, the Nordic Council agreed to in the upsilon region. The integrated the establishment of Nordita, togeth­ luminosity was about 600 inverse er with a liaison body for atomic en­ nanobarns. Using this data, the mass ergy affairs. Before Nordita. This 1931 photograph, of the upsilon was found very near taken in the auditorium of the Copenhagen At its first meeting on 25 June Institute for Theoretical Physics at one of the value determined by the Novosi­ 1957, the Nordita directorate el­ its annual congresses, shows in the front birsk group in an absolute precision row from the left: O. Klein, N. Bohr, measurement (see October issue, ected Niels Bohr as Chairman and W. Heisenberg, W. Pauli, G. Gamow, Torsten Gustafson as deputy. Deci­ L. Landau and H. A. Kramers. page 325). The Crystal Ball value is based on beam energy data from the machine group (no depolarization measurements for an absolute cali­ bration are yet available). At present ARGUS and Crystal Ball are running at DORIS-II energies around the upsilon (9.45 GeV), be­ fore starting work at the somewhat higher energies now available. The peak energy is now 5.6 GeV per beam. The mean luminosity over lon­ ger periods of time is continuously improving. There were initially some

CERN Courier, December 1982 409 Current line-up of detectors in the machines at DESY. The 60 r.f. accelerating cavities are now distributed symetrically in the PETRA ring, and the power supply has been boosted. problems due to the vacuum system, and the mean luminosity was not reaching the expected values. Four acceleration cavities had to be ex­ changed due to chemical effects on their walls. However the other excel­ lent properties of the machine were not affected. A particular advantage of DORIS-II is the short time required now for the injection of both elec­ trons and positrons. The DORIS-II ring is also being used for experiments with synchro­ tron radiation. About one third of the running time is devoted to this task. The specialized HASYLAB laborato­ ry now has 22 fully installed irradia­ tion facilities in its big hall. In addi­ tion, five installations of the Euro­ pean Molecular Biology Laboratory and one beamline providing radiation to the bunker of the Frauenhofer Ge- sellschaft continue to be available. The latter is mainly used for the in­ vestigation of X-ray lithography. At the PETRA storage ring several important modifications were car­ ried out this summer. The major im­ provement to the machine consisted of doubling the power supplied to the accelerating cavities. The 60 PETRA cavities are now symmetrically di­ stributed, and are powered by 8 transmitters, each of them provid­ ing 1 Megawatt, produced in two klystrons. This now provides 1.4 times the voltage previously availa­ ble to accelerate particles. The final effect should be an increase of the peak energy of the beam of about ten per cent. PETRA will then surpass 20 GeV per beam. However tests have been delayed due to a failure in the external power supply network. Tests at lower energies have shown

The ARGUS group on the roof of their control room, after celebrating the positioning of their detector in the DORIS-II ring, seen in the background.

(Photo DESY)

410 CERN Courier, December 1982 A hadronic event as seen by the Crystal Ball detector, newly installed in the DORIS-II ring at DESY. Each triangle represents one of the sodium iodide counters in the spherical detector.

tum resolution. In addition, the for­ ward and backward spectrometers were adjusted to the requirements of PETRA's minibeta quadrupoles and to the absence of solenoid compen­ sation coils. As approved by the DESY Physics Research Committee in its Septem­ ber session, CELLO will now remain in place at least up to the end of 1984. PLUTO, which has been active at the DORIS and PETRA machines since 1974, will be used to test (with cosmic rays) a newly developed drift chamber system. The last runs at PETRA were very successful and the PLUTO group is now busy analysing the collected data, in particular the reactions produced in photon-pho­ ton collisions. PLUTO had been pre­ pared for these investigations with the addition of two magnetic spec­ trometers in the forward and back­ ward regions. Between January and August 1982, each of the four PETRA inter­ that there are no intrinsic problems. It beam depolarization method. The action regions received a total inte­ was also possible to try out four of degree of polarization (in general 60 grated luminosity of 51 inverse pico- the new seven-cell cavities which to 70 per cent) is measured using barns. About 75 to 80 per cent of provide improved acceleration capa­ recoil photons from laser light. The this was finally used by the JADE, bilities compared with the five-cell depolarizing resonance is found with MARK-J, PLUTO and TASSO exper­ ones used at present. The four sev­ the help of small radial magnetic field iments. en-cell units were left in place and oscillations produced with the mag­ The TASSO apparatus (Hall SE) form part of the total complement of nets of the PETRA feedback sys­ was improved this year. Forward 60 cavities. tem. and backward spectrometers and a The superconducting cavity built During PETRA's summer shut­ vertex detector were added. The at the Kernforschungszentrum Karls­ down, the PLUTO detector was re­ vertex detector includes eight layers ruhe (Kf K) was tested earlier this year moved from the NE interaction re­ of drift chambers and is integrated in Hall W at PETRA (see June issue, gion and the big CELLO detector was with a new beryllium vacuum pipe. page 176). These tests were very moved in again. During the PLUTO No major hardware changes were successful and have been com­ run (which began in September made at the two remaining detectors pleted (see page 415). The cavity is 1981) the CELLO detector was im­ JADE and MARK-J. Already at be­ back in Karlsruhe. In PETRA's Hall E, proved in several ways. The granu­ ginning of this year, MARK-J had its new tests of superconducting cavi­ larity of its big lead liquid argon drift chamber tubes extended down ties in collaboration with CERN are shower counter (electromagnetic ca­ to about 10 degrees to the beam, now being prepared. A five-cell cav­ lorimeter) was increased by 50 per therefore improving the coverage of ity from CERN, operated at 500 MHz, cent by conveniently rearranging its solid angle. should be installed in January. cells. A beam pipe counter was ad­ The four PETRA interaction re­ The absolute energy of the PETRA ded. It consists of two layers of drift gions are equipped with minibeta beam and other important parame­ tubes and provides precise vertex quadrupoles. Space for these qua­ ters can now be measured using the reconstruction and better momen­ drupoles was made available by

CERN Courier, December 1982 The detection system at Intersection 8 of the CERN Intersecting Storage Rings, with its walls of uranium/scintillator hadron calorimeter, a good example of the sophisticated instrumentation now available at the ISR.

(Photo CERN 221.7.82) eliminating the solenoid compensa­ tion coils. The required compensa­ tion of the solenoid fields of the de­ tectors is done between CELLO, JADE and TASSO by an appropriate orientation and adjustment of the fields (see July/August 1981 issue, page 237). In fact CELLO has a field twice that of JADE and TASSO. All three fields are oriented in the same sense, as seen by a beam particle orbiting around the ring. At DORIS-II, the field of the ARGUS solenoid had to be compensated locally, since there is no field on the opposite side at the Crystal Ball. At present, in addition to the data- taking by the six big high energy groups (ARGUS, CELLO, Crystal Ball, JADE, MARK-J and TASSO) and to the HASYLAB investigations with synchrotron radiation, there is in­ creasing activity at DESY to prepare hardware for the proposed HERA machine. Superconducting proto­ type magnets are being tested, a 400 Watt liquid helium cryosystem violent (high transverse momentum) The ISR also enables identical de­ installed and several study groups collisions to the clear clustering of tectors to make a direct comparison are looking at details of the project. hadrons seen this year in calorimeter of proton-proton and proton-anti- experiments (see October issue, proton interactions. This is an acid page 327). These clusters ('jets') test of quark behaviour and could have also been seen at the SPS pro- throw considerable light on the CERN ton-antiproton collider. nature of the fundamental interac­ Twilight of the ISR The SPS collider probes a much tions. The antiproton runs with the higher energy, but the ISR has other ISR so far have really only scraped The lifetime of the Intersecting Stor­ attractions. Its luminosity (collision the surface of some rich physics. age Rings at CERN is being curtailed rate) is much higher. It can cover a Now that clear jets have been in order to liberate money, manpow­ range of collision energies. And the seen, the existing detectors at the er and space for the construction of measurable momentum fraction car­ ISR can envisage a full programme of the LEP electron-positron ring. How­ ried by the produced hadrons is high­ jet investigations. Systematic study ever the ISR is in the midst of an er than that at the SPS collider. The of these jets provides a good testing active experimental programme and ISR and the SPS collider therefore ground for quark/gluon (strong inter­ in a special meeting on 20 Septem­ cover different, and very much com­ action) theory, and the ISR will con­ ber, physicists met to discuss how plementary, kinematical regions. tinue to provide useful information to make best use of the remaining According to our present knowl­ right up to the minute it is switched time available on this unique ma­ edge of quark and gluon distributions off. chine. inside nucleons, gluons dominate at The ISR has had a monopoly of It took a decade of detector im­ lower momentum fractions. This direct photon physics, which investi­ provements at the ISR to go from the means that the SPS is predominantly gates the electromagnetic radiation first evidence for anomalously high a gluon-gluon collider, while the ISR (photons) coming from excitation of yields of secondary particles from can probe quark-quark scattering. the (electrically charged) quarks. The

412 CERN Courier, December 1982