ISOLDE EXPERIMENTS COMMITTEE
Minutes for the Seventeenth meeting on
12 February, 1996
 
 

OPEN SESSION

The ISC Chairman, Achim Richter, first welcomed Dr. Doris Forkel as the new ISOLDE Coordinator and expressed pleasure in her appointment to this demanding task. He also thanked the retiring Coordinator,
Dr. Olof Tengblad, for his excellent handling of the ISOLDE programme during the past three years.
Prof. K. Heyde of Ghent then intervened with the news that Prof. Richter has himself been awarded an honorary doctorate at that university on March 22, 1996.

Helge Ravn, ISOLDE Technical group leader, presented a detailed report on past and future ISOLDE operations and status.The general purpose separator GPS) continued to work well in 1995, while the high resolution separator HRS) produced its first radioactive ions, with 81% transmission to the tape station. The new robots have been installed and tested, while 30 targets were delivered in 1995. In 1996, the HRS will undergo further commissioning to make it more user-friendly although it is already available for certain target-test experiments.

A solution involving staggered extraction from the Booster has been found to the problems with molten metal targets. If adopted, this Booster mode would enable the full proton beam to be used on the target. Studies of the effect on the ISOLDE programme of the suggested Booster energy increase from 1.0 GeV to 1.4 GeV have revealed that this will be a clear asset for nuclei far from stability, while the slight loss in efficiency for nuclei near stability can be offset by using longer targets. In 1996 the high quality of beams and targets maintained in 1995 can be expected to continue.

The Chairman congratulated H. Ravn and his colleagues on the excellence of these results and then suggested that the ISOLDE community carefully considers the effect of the Booster energy increase on
their plans.

In her Coordinator's report, D. Forkel revealed that of the 53 experiments so far scheduled, 12 have been finished, while of a further seven test experiments one has been completed. This programme involves
93 institutes from 22 countries with a total of 300 participants. In 1995, 249 good radioactive beam shifts were delivered along with 80 stable shifts, and this level of performance will be continued in 1996. The outstanding number of allocated shifts fell steadily during 1995 and will continue to do so in 1996.

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

1. Identification and decay studies of new, neutron-rich isotopes of bismuth, lead and thallium by
    means of a pulsed release element selective method; CERN/ISC 96-1/P76: K.Rykaczewski.

2. Search for detour transitions in the radiative EC decay of 81Kr; CERN/ISC 96-2/P77; M.Pfützner.

3. Single-neutron states in 133Sn: Status report and beam time request IS338);
     CERN/ISC 96-6/P53 Add.1; P.Hoff.

4. Neutron-rich silver isotopes produced by a chemically selective laser ion-source: Status report
    on experiment IS333 part II and request for beam time; CERN/ISC 96-4/P34 Add.1; K.-L.Kratz.

5. Nuclear electrical and optical studies of hydrogen in semiconductors IS345):
    CERN/ISC 96-3/P65 Add.1; D.Forkel-Wirth.

CLOSED SESSION

Present: B. Allardyce, G. Bollen, J. Eades Secretary), D. Fick, D. Habs, L. Foà, D. Forkel-Wirth,
              A. Mueller, E. Moya de Guerra, H. Nifenecker, H. Ravn, A. Richter Chairman),
              K.Riisager, F.-K Thielemann.

Apologies: G. Goggi.

The Chairman first expressed his appreciation of the hard work of O. Tengblad during his three-year tenure as ISOLDE Coordinator. He welcomed the new Coordinator, Doris Forkel-Wirth and assured her of the committee's support for continuing O. Tengblad's successful work. The minutes of the previous meeting were then approved.

The Letter of Intent ISC 95-30/I18 73Ge Moessbauer spectroscopy in semiconductors: ISC 95-30/I18) was briefly discussed. The authors ask for a four-shift test of the general method before submitting a proposal. It was agreed that this test could be allocated from the Coordinator's reserve and that D. Forkel and H. Ravn would arrange this at a suitable time.

Some discussion of the Technical group leader's report then followed. The committee agreed that the increase of the Booster energy to 1.4 GeV in 1999 would be a clear net benefit to the ISOLDE community. However, the problem of finding the 200kCHF needed for the beamline power supply remains, and the committee asked the CERN Research Director, Lorenzo Foà, to investigate the possibilities for finding this sum. Concerning idea of staggered extraction of proton pulses from the four Booster rings to allow full proton intensity on the molten metal targets, the committee strongly endorses this as a goal for 1997, especially since several experiments that require full intensity are awaiting beam time. L. Foà agreed to investigate the problem of finding the necessary 100 kCHF for beam transformers, etc.

The committee then proceeded to discuss the proposals presented in the Open meeting.

P76: Identification and decay studies of new, neutron-rich isotopes of bismuth, lead and thallium by
        means of a pulsed release element selective method

The use of the pulsed proton beam structure in these new studies of neutron-rich isotopes near the doubly-closed 208Pb region has been extremely rewarding from the physics point of view. In addition, it represents an interesting new technical development, the results from which would complement those from GSI, where masses and charges are readily obtainable but no spectroscopy is possible. The proposal will therefore be recommended to the Research Board for the eight shifts requested.

P77: Search for detour transitions in the radiative EC decay of 81Kr

The committee found that it would be interesting to complement the 41Ca case with studies of the additional case of 81Kr , although it is clear that the theoretical interpretation of the data will be much more difficult than in calcium. It was clear that every effort should be made to obtain the highest efficiency of the target and ion source system in order to reduce the collection time as far as possible. As a substantial reduction was thought to be quite possible, the committee will recommend to the Research Board that the experiment be scheduled for ten shifts instead of the requested fifteen.

P53 Add.1: Single-neutron states in 133Sn: Status report and beam time request IS 338)

It was thought that the first run of P53 to measure the single-neutron state in 132Sn had been an impressive success. To clarify some of the outstanding questions, this work should evidently be extended by the 5-shift half-life measurement and the 5-shift 132In measurement. However the need for 20 shifts for the 134In was questioned, as it was thought that a higher detection efficiency could be obtained by optimising the experimental setup.

For the moment only ten shifts will therefore be allocated, and the committee will consider the 134In measurement again after a report has been made on this possibility.

P34 Add.1: Neutron-rich silver isotopes produced by a chemically selective laser ion-source:
     Status report on experiment IS333 part II and request for beam time

The committee considered that the proposed new measurements would represent an important contribution to astrophysical knowledge but that technical problems uncovered in running the previous experiments remain to be solved. Before allocating a definite number of further shifts, the committee will therefore await a report on the improvements mentioned in the present Addendum in connection with shielding the gas-laser discharge, etc.

P65 Add.1: Nuclear electrical and optical studies of hydrogen in semiconductors IS345):

The committee was satisfied that this large group had the strength and experience to carry out this rather extensive and important series of studies of hydrogen in semiconductors. The requested 35 shifts in fact represent an efficient way of using available targets and will be allocated as requested.

Other Business

Professors S.V. Harissopulos and G.S. Anagnostatos of the Hellenic Nuclear Physics Society in Athens have expressed the interest of the Greek community in collaborating in the ISOLDE programme. It was decided to encourage this possible future extension of the reach of the ISOLDE community.

Dates of next meetings: