After opening the meeting, the Chairman called on the ISOLDE technical group leader to report on progress. H. Ravn indicated that more protons were delivered onto targets in 1997 than ISOLDE was initially entitled to, the CERN management having decided, when fire had prevented other facilities from running, to run additional protons to ISOLDE and to exempt ISOLDE from "critical day" restrictions. Together with commensurate efforts by outside and in-house groups, this turned the originally inauspicious expectations for 1997 into what has certainly been the most productive PSB ISOLDE year yet. Among several successful new operational aspects were the introduction of the first beamlines to the extended experimental hall, an improvement of the HRS resolution to 15000, and a laser ion source performance allowing 107g,107m Ag isomer separation and the production of beryllium isotopes over the atomic mass range 7 to 14.
The Chairman congratulated both the CERN management and the ISOLDE team for the efforts that resulted in these many successes.
The ISOLDE coordinator, D. Forkel-Wirth, then presented her report, describing first the installation of Nicole and Mistral completed in 1997) and the REX trap beamline which although begun in 1997, is to be completed in 1998). In reviewing the ISOLDE programme's successes in 1997, she noted that 315 shifts had been delivered to 31 experiments out of the agreed total of 400. Nuclear physics experiments are still, at 41% of this total, the main users of ISOLDE beams, with 24% going to solid-state physics, 19% to atomic physics, 10% to particle and astrophysics and 6% to medical and biological studies. The 1998 run period will start on April 15 and run until December 8.
The Chairman thanked Dr. Forkel-Wirth, who was attending her last ISC meeting as ISOLDE coordinator. He noted her impressive achievements on behalf of all branches of the ISOLDE physics programme during her term of office, and expressed the gratitude of the entire ISOLDE community for these.
Presentations were then made of the following proposals and progress reports:
1. Beta-decay study of n w excitations in
neutron-rich fp) nuclei.: Test of the empirical nuclear
interaction; CERN/ISC 97-23/P92; G. Walter.
2. Structure features of 6He from direct reactions on light
target nuclei; CERN/ISC 97-25 /P93;
3. Beta-decay of 47Mn; extension of systematics of MT
= 3/2, odd-Z nuclei to fp- shell;
CERN/ISC 97-26/P94; A. Jokinen.
4. Study of the 163Ho-decay for a neutrino mass experiment; CERN/ISC 97-28/P95; M. Altmann.
5. Nuclear spectroscopy with copper isotopes of
extreme N/Z ratios; CERN/ISC 96-31/ISC/P96;
6. Status report and proposal for continuation IS304): Measurement
of nuclear moments and radii
by collinear fast-beam laser spectroscopy; CERN/ISC 97-29/P9 Add.2; R. Neugart.
7. IS302: High-accuracy mass determination of
unstable nuclei with a Penning trap mass spectrometer;
CERN/ISC 97-30/P6 Add.2; G. Bollen.
Present: B.W. Allardyce, R. Ammerlaan, G. Bollen,
J. Eades Secretary), D. Fick, W. Gelletly,
H. Wenninger replacing L. Foà), D. Forkel-Wirth, D. Habs, H. Ravn,
A. Richter Chairman), G. Sletten.
Apologies: L. Foà, F-K. Thielemann, K. Peach.
The minutes of the twenty-first meeting were approved without change.
The commmittee noted with satisfaction of the impressive advances reported on all fronts by the ISOLDE technical group leader, and congratulated H. Ravn and his colleagues on these achievements. Especially noteworthy was the total of 315 radioactive beam shifts delivered at the PSB ISOLDE in 1997, this being well above the number predicted a year ago. This occurred in spite of the severe problems connected with recent budgetary restrictions and massive departures of CERN staff. H. Ravn pointed out that the positive results could be attributed to three factors: help from the ISOLDE outside groups, supplementary efforts on the part of the in-house ISOLDE group, and the CERN management's constructive attitude to solving the problems referred to above.
H. Wenninger agreed that the first two factors were a crucial but exceptional response to a crisis situation, and assured the committee that the CERN management fully recognises the importance of the ISOLDE programme in the coming years. He said that a solution is now envisaged to ensure that all necessary technical support is available in the future, especially in the critical domain of vacuum support.
The committee was equally pleased with the report of the outgoing ISOLDE Coordinator, Doris Forkel-Wirth, who had responded to the difficult 1997 scheduling situation by carefully organised logistics and efficient use of the available time. The result was that a large number of experiments could be accommodated in all domains of ISOLDE research. The Chairman expressed the indebtedness of the committee and the ISOLDE community in general to Dr. Forkel-Wirth for her patient and good-humoured efforts in shaping the ISOLDE programme, first from May 1990) as a member of the ISOLDE team, and then from January 1996) as coordinator, and wished her well in her new TIS division appointment.
The closed meeting continued with a discussion of the proposals and progress reports presented in the open session, as follows:
Since proposals P92, P94 and P96 were of similar aims they were discussed together.
P92: Beta-decay study of n w excitations in neutron-rich fp) nuclei.: Test of the empirical nuclear interacton
The proposed decay studies were thought to be
well suited to the goal of testing shell-model calculations far from stability.
As the proposal represents
a rather extended programme covering Ca, Si, and Fe daughter nuclei, it
was decided to recommend to the Research board the allocation of 15 shifts
initially, with priority assigned to the Si case.
P94: Beta-decay of 47Mn; extension of systematics of MT = 3/2, odd-Z nuclei to fp-shell
As in the case of P92, the proposed nuclear structure studies in the region far from stability represent good physics concerning one of the key interesting issues that ISOLDE can address. However there are a few outstanding technical questions concerning for example the potassium background and the quantity of 47Mn that can be produced. This suggests that it will be sound practice to schedule a three shift test before seeking Research Board approval for the full programme. The committee also noted that the proposal relies heavily on the use of the laser ion source, but that none of the experts who have developed and tested this are among the collaborators. The ISC therefore urges the collaboration to bring this expertise into the collaboration.
P96: Nuclear spectroscopy with copper isotopes of extreme N/Z ratios
The ISC was of the opinion that the experiment should result in important physics on both the neutron-deficient and the neutron-rich sides and represents a useful complement to similar studies to be undertaken at GSI. The proposal evidently also points to future applications in the form of experiments with REX-ISOLDE. The Chairman will therefore recommend an initial allocation of 24 shifts for these experiments by the Research Board.
P93: Structure features of 6He from direct reactions on light target nuclei
After some discussion, the committee concluded that as it stands the proposed experiment could at best test reaction mechanisms, and not the structural aspects of 6He, for which as pointed out in reference 4 of the proposal) the 6He energy would have to be far above the Coulomb barrier. It appears that single particle transfer reactions would be better suited for this. The committee nevertheless thought that 6He structure experiments would be of interest and encouraged the collaboration to find better ways of carrying them out.
P95: Study of the 163Ho-decay for a neutrino mass experiment
The committee recognised that low temperature calorimetic detectors are now being used in such fields of particle astrophysics as WIMP searches, and that they are at a stage of technical development that may make them useful for precision experiments on the neutrino mass. Some reservation was expressed however about the value of an upper mass limit of 150 eV/c2 as an improvement on previous CERN experiments of this nature. The collaboration will therefore be allocated five shifts for testing the technique, with special emphasis on answering questions about radiation damage, after which a progress report should be presented.
P9 Add. 2: Status report and proposal for continuation IS304): Measurement of nuclear moments and radii by collinear fast-beam laser spectroscopy
It was agreed that the IS304 collaboration has carried out a very professional investigation on the nuclear spectroscopy of Na isotopes, and that these represent one of the ISOLDE highlights of the last few years. The IS304 programme should therefore continue as requested in the progress report, with a further allocation of 32 shifts. These should be concentrated on a thorough investigation of Ne, with Be istopes clearly also in the forefront. However, further research along these lines will have to be justified with a new proposal instead of further Addenda.
P6 Add.2 IS302): High-accuracy mass determination of unstable nuclei with a Penning trap mass spectrometer
As with IS 304, the IS302 collaboration has shown
itself capable of doing first rate work in its domain, producing high precision
results on the masses of many isotopes with its Penning trap technique.
IS302 will therefore be allocated a further 32 shifts for the work described
in the Addendum, once more on the understanding that further extensions
will require a fully-fledged new proposal.
The committee took note of two Letters of Intent , ISC 97-27/I27 Study of neutron-dripline nuclei using post-accelerated ion beams) ISC 97-32 /I28 Self-Diffusion of Nitrogen and Carbon in Amorphous Precursor Ceramics).
G. Huber, Chairman of the ISOLDE Collaboration Committee, has announced that the European Community has agreed to fund ISOLDE as a large-scale facility at a level of 314.000 ECU, perhaps as early as April 1998. This entails legal and economic responsibilities of a body that is independent of CERN and is able to enter into a formal contract with the EC. This may be done by constituting an "ISOLDE European Economic Interest Group". Details may be obtained from Prof. Huber, Universität Mainz.
It is expected that the committee's strength will be reinforced by the addition of two new members from the first meeting of 1998.
It was announced that Thomas Nilsson, from Chalmers University, Gothenburg, will take over the job of ISOLDE coordinator from 1 February 1998.
The dates of the ISC meetings in 1998 are: