ISOLDE EXPERIMENTS COMMITTEE
Minutes for the twenty-fifth meeting on
Monday 30 November 1998

OPEN SESSION: Monday, 30 November, at 14.00 h, Main Auditorium.

A. Richter first expressed his thanks to L. Foà whose term as CERN Research Director is about to end) for his many efforts on behalf of ISOLDE, and wished him well on his return to research. L. Foà replied with a short appreciation of the ISOLDE community as a splendid example of scientific cooperation, and praised its community spirit as well as the efficiency of the ISC in carrying out its work during his term of office.

The Chairman also welcomed C. Détraz, who from January 1, 1999 will take over the office of Research Director, and P. Walker, who begins a two year membership of the ISC with the present meeting. He also announced that D. Fick, D. Habs and F.-K. Thielemann had agreed to continue as members until July 1999.

The meeting continued with the report of H. Ravn, ISOLDE Technical Group Leader. He summarised the various aspects of ISOLDE operation in somewhat more detail than usual owing to the cancellation of the September meeting. Some 23 targets were produced in 1998; these involved 40 target changes in a programme that delivered 255 General Purpose Separator GPS) shifts and 20 High Resolution Separator HRS) shifts to ISOLDE users.

The HRS figure is one reflection of the severe constraints under which CERN in general and ISOLDE in particular is now suffering as a result of manpower and budgetary difficulties. The cumulative result of these restrictions over the period 1997-1999 is that no scheduled operation or development of the HRS is presently foreseen by the Technical Group Leader. The major argument for the installation of the HRS having been to increase the overall number of shifts available to ISOLDE users, the 1999 level of operation will consequently not be improved relative to the 1998 situation.

T. Nilsson, the ISOLDE Coordinator then presented the year 1998 from the scheduling point of view. After listing the favourable and unfavourable influences at work, he showed some of the key results from a year in which 23% of the ISOLDE shifts were devoted to solid state physics, 38% to weak interaction and nuclear physics, 12% to particle and astophysics, 4% to biology and medecine, and 23% to atomic physics.

The open meeting was concluded by presentations of the following new ISOLDE proposals:

ISC/98-20/P103: Studies of the Beta Decay of Kr and Sr nuclei on and near the N=Z line with a Total Absorption Gamma Ray Spectrometer; jointly presented by Ph. Dessagne and B. Rubio.

ISC 98-22/P104: Semiconductor Spectroscopy with short lived Isotopes; presented by M. Deicher, who also remarked on the valuable role played in the past two years by A. Burchardas Coordinator of solid state experiments, and who is now departing to take up a position in Munich.

ISC 98-23/P105: Investigations of neutron-rich nuclei at the dripline through their analogue states: The cases of 10Li-10Be T=2) and 17C-17N T=5/2); ISC 98-23/P105; presented by B. Jonson.

ISC 98-19/P102: Self-Diffusion of Carbon and Nitrogen in the Amorphous Ceramics Si26C41N33 and related Materials; ISC 98-19 /P102; presented by W. Frank.

CLOSED SESSION

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

Apologies: G. Sletten

After a few words of welcome from the Chairman to C. Détraz and P. Walker, the ISC approved the minutes of the 24th meeting without change. In discussing the Technical Group Leader's report, the committee placed on record its appreciation of the high quality performance of ISOLDE during 1998 and its recognition of the debt owed to H. Ravn and T. Nilsson in bringing this about. As remarked upon by H. Ravn in his talk, the 255 GPS shifts and 20 HRS shifts delivered in 1998 were achieved against a background of severe budgetary and manpower restrictions. In spite of this, 1998 has turned out to be a good and productive year for ISOLDE. However the committee noted that the above-mentioned restrictions have hindered the development of the HRS and are likely to become more rather than less severe in future. It therefore called for a joint assessment by the CERN Management, the ISOLDE Collaboration and the CERN Technical Group of the human and financial resources needed if the requirements of a) groups who presently intend to use the HRS, and b) those who might wish to use it if various technical improvements were to be carried out, are to be fulfilled. All interested collaborations are therefore urged to make their needs known to the CERN technical group, so that future priorities and timetables can be planned. A relevant point in this respect is that CERN has already instigated the procedure for hiring a fourth engineer, whose presence from mid-1999 should alleviate the situation to some extent.

Concerning the ISOLDE Coordinator's report, it was again remarked that in spite of the current difficulties ISOLDE has managed to maintain a profile of high quality research throughout the year, as was evident in Thomas Nilsson's choice of key results from the year's activities to illustrate his talk.

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

P103: Studies of the Beta Decay of Kr and Sr nuclei on and near the N=Z line with a Total Absorption Gamma Ray Spectrometer

The committee found the proposed study of Gamow-Teller strengths in N=Z nuclei to be interesting and worthwhile with the proposed gamma-ray calorimetry method, although there was some concern on the feasibility of disentangling quenching and shape changes. The committee will therefore propose to the Research Board that the experimenters first concentrate on 71Kr characterised by a wide energy window) and 73Kr characterised by large prolate-oblate separation) in an initial 12-shift beam allocation. A progress report may then be followed by further beam time allocations.

P105: Investigations of neutron-rich nuclei at the dripline through their analogue states:
The cases of 10Li-10Be T=2) and 17C-17N T=5/2)

The study of neutron-rich nuclei near the dripline via analogue states was thought to be timely, and the inverse kinematic technique, having already been proven with protons impinging on 10C, to be novel and worth trying for the 9Li and 16C cases. Recognising also that the proposed experiment is ideally suited to REX-ISOLDE because of its range of beams and energies, the committee will recommend to the Research Board an initial 12 shift allocation for 9Li, with conditional approval for the remaining 20 shifts after a successful progress report.

P104: Semiconductor Spectroscopy with short lived Isotopes

The committee saw the advantage of complementing the group's past studies of semiconductor defects in long-lived isotopes with new measurements of short-lived ones under improved experimental conditions, and approved an allocation of 24 shifts for these studies over a two year period. However, the scheduling of these shifts will be contingent on a technical feasibiblity study of the local laboratory necessary for these studies, made in collaboration with such CERN services as the technical inspection and safety group TIS) and the ISOLDE technical group. No Research Board approval was thought necessary for this allocation since the physics of the proposal has already been explained in detail to the Research Board in connection with experiment IS357 CERN/ISC 96-15/ISC P81, 22 April 1996, CERN/DG/Research Board 96-243, Minutes 127, 13 June 1996).

P102: Self-Diffusion of Carbon and Nitrogen in the amorphous ceramics Si26C41N33 and related materials

The committee was in some doubt about certain unclear aspects of the proposed experiment such as why the particular ceramic Si26C41N33 is of interest, and what specific meaning is to be attached to the term `amorphous' in the context of the proposal. In the interests of fairness it therefore decided to call on the opinion of an external referee before considering the proposal further.

OTHER BUSINESS

The committee took note of two letters of intent:

ISC 98-17/I29: Investigation of the impact of the 39Arn,a)36S reaction on the nucleosynthesis of the rare isotope 36S; C. Wagemans.

ISC 98-21/I30: Search for new Physics in Beta-neutrino correlations using trapped ions and a retardation spectrometer; D. Beck.

The Chairman has received a postdeadline progress report and request for 8 additional shifts from IS 358. The committee recognised the quality of the results described therein and is in principle favourable to the extension, but would welcome an addendum to the IS358 proposal in due course.

The dates of the 1999 ISC meetings are as follows: