ISOLDE EXPERIMENTS COMMITTEE
Minutes for the twenty-seventh meeting on
Monday 3rd May, 1999

OPEN SESSION

The CERN Research Director, C. Détraz opened the meeting with a short appreciation of the outgoing ISC Chairman A. Richter. He said that A. Richter's role had been predominant not only within the ISC itself but also in presenting the Committee's recommendations with great persuasiveness and elegance to the Research Board and the Scientific Policy Committee. The clarity of his arguments indeed brought the breadth, depth and value of the ISOLDE programme to the attention of a wide audience, and for this, CERN in general, as well as the ISC, is indebted to him.

The Chairman then invited the ISOLDE Technical Group Leader, H. Ravn, to present his report. He reported on several improvements in the domains of the General Purpose Separator, the beam lines, the vacuum system and the control system. Concerning target production, the radiochemical class B laboratory for which a TIS technician is now available has been refurbished, and a mode of installation of REX ISOLDE has been found that interferes only minimally with the experimental programme. H. Ravn also reminded the meeting of the constraints referred to in the last meeting of the ISC, which mean that only 200 eight hour GPS shifts will be available in 1999. He announced that meetings have begun with the management to find ways of improving this situation, and that a new mechanical engineer started work on 16 April. Furthermore a selection board for a fourth engineer in charge of operation will be scheduled soon. Among other matters of interest, major improvements in the 11Li beam intensity have resulted from the tests undertaken with the Rutherford Laboratory on thin tantalum-foil targets.

Thomas Nilsson then presented a short Coordinator's report in which he indicated that the 1999 startup has been very trouble-free and that the tantalum foil tests and MISTRAL runs have been very successful. He then presented the latest version of the 1999 schedule, which in fact differs very little from the previous ones.

A. Richter thanked C. Détraz for his previous kind remarks concerning his Chairmanship, and also thanked the numerous Committee and ISOLDE community members for their unfailing support during his six-year term of office. He also expressed his conviction that ISOLDE will survive and prosper if experiments of the present high scientific standard continue to be carried out.

Presentations were then made of the following proposals and progress reports:

1. High-resolution spectroscopy of Sr and Y nuclei near the N = Z line; CERN/ISC 99-12/P110; M. Oinonen.

2. Interface magnetism investigated with radioactive atoms; CERN/ISC 99-2/P106;  H.H. Bertschat.

3. Beta-decay studies of dripline isotopes of Be; CERN/ISC 99-16/P99 add.1, CERN/ISC 98-6/P99;
    U.C. Bergmann.

4. Investigations of nuclei close to the neutron dripline: Ne and Na and 8He; CERN/ISC 99-11/P109;
     K. Wilhelmsen Rolander.

5. Spectroscopy of 100,102 Pd by means of electron conversion and g- g correlation measurements;
     CERN/ISC 99-15/P112; P. Sona.

6. Search for new physics in beta-neutrino correlations using trapped ions and retardation spectrometer;
     CERN/ISC 99-13/P111, CERN/ISC 98-21/I30; D. Beck.

7. Progress report and beam time request to the ISC IS364): Beta-decay study of nhw excitations in
     neutron-rich fp) nuclei: Test of the empirical nuclear interaction; CERN/ISC 99-14/P92 add.1,
     CERN/ISC 97-23/P92; G. Walter.

At the end of the open session, G. Huber, on behalf of the entire ISOLDE Collaboration, rose to thank A. Richter for the invaluable services provided to the ISOLDE physics community during his term of office.

CLOSED SESSION

Present:   B.W. Allardyce, R. Ammerlaan, G.Bollen, C. Détraz, J. Eades Secretary), D.Habs,
                P. Van Isacker, K-L Kratz, J. May, T. Nilsson, H. Ravn,  A. Richter Chairman),
                G. Sletten, R. Voss for G. Goggi), P. Walker.

Apologies: D. Fick, F-K. Thielemann.

The minutes of the 26th meeting were approved without change. The Committee noted with pleasure the good news of H. Ravn concerning the improved 11Li yields a factor 2, which may yet improve to a factor 10) and that of T. Nilsson concerning the early successes of the ISOLDE programme in 1999. It was stressed that good target development is essential to ISOLDE. In view of the limited number of GPS shifts and the ever increasing number of shifts now being requested it was thought that it would be useful to arrange a general review of the already agreed ISOLDE programme, similar to the one held at Leysin some years ago.

The closed meeting then continued with a discussion of the proposals and progress reports presented in the open session, as follows:

P110: High-resolution spectroscopy of Sr and Y nuclei near the N = Z line

The ISC thought that the high resolution spectroscopy and mass measurements of nuclei near the N=Z can be extremely worthwhile. The spectroscopic part of the experiment should make an important contribution to our knowledge of these nuclei, while the accurate mass measurements should also answer a real need in the astrophysical domain. The Research Board will therefore be asked to approve a 20-shift allocation.

P106: Interface magnetism investigated with radioactive atoms

It is clear that the proposal follows an interesting trend in the study of magnetic materials away from bulk measurements and towards lower-dimensional systems. The collaboration also has proven its ability to carry out previous proposals as evidenced by three recent P.R.L. publications. The Committee therefore will suggest that the Research Board allocate the full request of 22 shifts to the experiment.

P99 Add.1: Beta-decay studies of dripline isotopes of Be

The Committee felt that the present addendum describing results of a previous allocation of shifts had, as requested, demonstrated the success of the suggested line of work, and re-emphasizes the case for measuring dripline isotopes of 12Be and 14Be. Allocation of the outstanding 24 shifts will therefore be supported by the Chairman at the Research Board.

P109: Investigations of nuclei close to the neutron dripline: Ne and Na and 8He

The Committee found that the case for both the 8He and the neutron-rich Ne and Na isotope measurements had been well made. The High Resolution Separator is required for the latter and for these cases, the somewhat low yields may be improved by the introduction of newer target technologies and a higher booster energy from which also proposal P92 below should benefit). The Committee therefore decided to recommend to the Research Board an initial allocation of 12 shifts for 8He, and 12 shifts to one of the Ne/Na experiments as a test. If successful HRS-related operation has then been demonstrated, the remaining allocation may be made.

P112: Spectroscopy of 100,102Pd by means of electron conversion and g-g correlation measurements

After reading the proposal and hearing the presentation the Committee was not convinced that a clear-cut physics case had been made that the proposed measurements on 100,102 Pd nuclei would indeed remove remaining ambiguities in mixed symmetry states. It will not therefore recommend scheduling the experiment to the Research Board.

P111: Search for new physics in beta-neutrino correlations using trapped ions and retardation spectrometer

It was generally agreed that the collaboration had made an impressive case for the proposed beta-neutrino experiments, which complement similar investigations at other facilities. The understanding and operation of the rather complicated apparatus will therefore be encouraged initially as a test experiment, consisting of 9 stable and 9 radioactive shifts, For the moment, no Research Board approval was thought necessary. After a progress report, the remaining full allocation may be given

P92 Add. 1: Progress report and beam time request to the ISC IS364): Beta-decay study of nw excitations in neutron-rich fp) nuclei: Test of the empirical nuclear interaction

The ISC took note of the results achieved by P92 IS364) in beta-decay studies of neutron-rich p-shell nuclei, and felt that indeed in some cases the nuclear state structure close to the ground state could be clarified by the proposed continuation and compared with shell-model calculations. However some questions exist concerning the spectroscopic studies of very low energy transitions, which might be better done with for example) a low energy photon counter. It was therefore decided to allow the 9 shifts requested for the Mg/Na/Al experiments, with the proviso that this allocation should be considered to terminate the experiment. Further requests should then be substantiated with a new proposal.

OTHER BUSINESS

In closing the meeting, the Chairman thanked all past and present members of the ISC for their support during his term of office, noting especially the contribution of the retiring members C.A.J. Ammerlaan,
D. Fick, D. Habs and F.-K. Thielemann. He also expressed his appreciation for the continuous and friendly support he has received over the years from the ISC Secretary, J.Eades.

G. Sletten has kindly agreed to continue in the ISC for another year.

The next ISC meeting is on 27-28 September 1999.