ISOLDE EXPERIMENTS COMMITTEE
Minutes of the eleventh meeting on May 16th , 1994
 

OPEN SESSION

The ISC Chairman, Achim Richter, first expressed his thanks to the retiring Research Director,
P. Darriulat, for the support and encouragement he has always shown to the ISOLDE physics
community and its research programme. The ISOLDE Technical Group Leader, H. Ravn then
presented a short report on the development of the laser ion source, which is now in a sufficiently advanced state to be tested in approved experiments. O. Tengblad, the ISOLDE Coordinator, briefly described the situation in the experimental hall, the programme of tests made with stable beams during
the recent shutdown period, and the status of the physics programme.

Presentations were made of the following proposals:

1. Addendum to proposal: Electrical activation of dopant atoms in the II-VI Materials M-X M=Zn,
    Cd and X=S, Se Te) Saarbrücken - Konstanz - CERN Collaboration); CERN/ISC 94-6/P40 Add.1;
    Th. Wichert.

2. Proposal: Emission channeling investigation of implantation defects and impurities in II-VI
     semiconductors CERN - Konstanz - Berlin - Groningen Collaboration); CERN/ISC 94-1/P59;
     S.G. Jahn.

3. Addendum to proposal : 111Cd- and 199mHg- Derivatives of Blue Oxidases Leipzig, Fakultät für
    Physik und Geowissenschaften - Martinsried MPI für Biochimie); CERN/ISC 94-2/P20 Add.1;
    W. Tröger.

4. Proposal: Emission channeling studies on the behaviour of light alkali atoms in wide-band-gap
    semiconductors Konstanz - Groningen - ISOLDE CERN Collaboration); CERN/ISC 94-9/P62;
    H. Hofsäss.

5. Proposal: Search for 73Rb and investigation of nuclear decay modes near the Z=N -line in the border
    region of the astrophysical rp-process path CERN - Gatchina - Jyväskylä - Lyon - Oslo - Strasbourg
    - Paris IN2P3 Collaboration); CERN/ISC 94-10/P63; Y. Novikov.

6. Proposal: Test of a high power target design RAL - CERN - Daresbury - Manchester - Surrey
    Collaboration); CERN/ISC 94-12/P64; J.R.J. Bennett.

7. Proposal: Laser spectroscopy of neutron rich bismuth isotopes CERN - Mainz - Manchester
     - Stony Brook Collaboration; CERN/ISC 94-7/P60; J. Billowes.

8. The dynamics of a -particle decay: Anisotropies and branching ratios in rare-earth nuclei CERN
     - Leuven - Liverpool - Lund - Manchester - Maryland - Oregon - Oxford - Prague Collaboration;
     CERN/ISC 94-8/P61; I.S. Grant.
 

CLOSED SESSION

Present: J.V. Allaby, J. Aystö, P. Darriulat, J. Eades Secretary), L. Foà, D. Forkel-Wirth,
              R. Helbig, W. Hillebrandt, A. Mueller, H. Ravn, B. Allardyce representing D.J. Simon),
              A. Poves, A. Richter Chairman), K. Riisager, O. Tengblad, P. Van Duppen.

Apologies: E. W.  Otten

The Chairman once again expressed the Committee's thanks to the retiring Research Director,
Pierre Darriulat for his constant and invaluable support of the ISOLDE facility and of the ISC, and welcomed his successor, L. Foà to his first ISC meeting. He also thanked the retiring members of the Committee, J. Aystö, E.W. Otten and A. Poves, for their hard work and good judgment in evaluating ISOLDE proposals over the last three years.

The minutes of the last meeting were approved with the correction that contrary to what was stated concerning P58 Emission channeling studies of the lattice site of oversized alkali atoms implanted in metals), this experiment is not the first metallic solid-state experiment at ISOLDE, but only the first study on implantation of alkali atoms into metals.

Discussion then took place as follows on the proposals presented in the open session.

P40 Add 1: Electrical activation of dopant atoms in the II-VI Materials M-X
                     M=Zn, Cd and X=S, Se Te)

In this addendum, 25 additional shifts were requested over two years in order to build on the results of the exploratory experiments done so far. These have shown the way ahead, although as yet no publishable results have been obtained. The Committee was favourable to this request, noting the high technical importance of the proposed measurements, particularly concerning the possibility of making a blue-emitting laser diode. The Chairman will therefore inform the Research Board of the continuation of P40 with a further 25 shifts of beam time.

P59: Emission channeling investigation of implantation defects and impurities in II-VI semiconductors

The Collaboration requests 26 shifts for emission channeling measurements, the topics selected being complementary to those proposed by P40. Several advantages arise from the use of the proposed two-dimensional position-sensitive electron detector, which it was noted has been developed at CERN. Three additional shifts are requested for testing this. The Committee was in favour of an initial allocation of 15 shifts out of the requested 26. These should be used for studies on Selenium and Cadmium, and should include 2-3 shifts for the electron detector tests which may be expected to speed up later measurements.

It was also felt that all groups studying II-VI semiconductors should be encouraged to hold a short workshop and present a common report to the Committee in the not too distant future. The Chairman will discuss this matter with the Spokesmen of the Collaborations concerned.

The Research Board will therefore be advised to allocate 15 shifts to P59, with the understanding that P40 and P59 will keep close contact during their beam time owing to their community of interests.

P20 Add.1: 111Cd- and 199mHg- Derivatives of Blue Oxidases

The Collaboration has requested 16 further shifts, for continuation of their studies of Cd and Hg derivatives of blue oxidases. The comittee has been impressed by the originality and quality of this work and does not hesitate to recommend the allocation of the time as requested.

P62: Emission channeling studies on the behaviour of light alkali atoms in wide-band-gap
         semiconductors

Thirty shifts for implantation studies of Li and Na in diamond and ZnSe have been requested by the P62 Collaboration. The general feeling was that once again there is common ground between this Collaboration and others in the semiconductor field in particular P59) and that a joint workshop will clarify common motives and future directions. The Committee therefore proposes allocation of 15 shifts for this work, noting however that the low yield of 20Na will mean that additional target tests will have to be done before any 20Na measurements can be scheduled.

P63: Search for 73Rb and investigation of nuclear decay modes near the Z=N -line in the border
         region of the astrophysical rp-process path

The request of the P63 Collaboration was for 28 shifts to search for 73Rb. While the existence of N~Z nuclides seems worthy of investigation, the possible astrophysical role of 73Rb was not thought to be the primary argument for the search proposed. It was nevertheless noted that the absence of 73Rb in previous searches including one at the old ISOLDE) does not necessarily mean that a new one would be unsuccessful, since the PSB ISOLDE has lower short-lifetime losses. It was thus thought appropriate to look at the 74Rb yield first, and to use the results to estimate the 73Rb yield. This will form the basis for a new evaluation of the proposal. It was therefore decided to allocate 6 shifts for this measurement, and to advise the Research Board appropriately later on the basis of the outcome.

P64: Test of a high power target design

The Committee was in no doubt about the technical interest of the tests proposed, and felt that CERN must offer all help to the international community in making the proposed test on a high power target for accelerated radioactive beams. The Research Board will therefore be asked to approve the scheduling of the six shifts requested.

P60: Laser spectroscopy of neutron rich bismuth isotopes

There was general agreement that the isotope shift and HFS measurements proposed in the region
210Bi to 214 Bi were both relevant and feasible with the well-known techniques proposed. The results should supplement those known already for the Pb isotopes. The experiment will therefore be recommended to the Research Board for scheduling at the 12-shift level requested.

P61: The dynamics of a -particle decay: Anisotropies and branching ratios in rare-earth nuclei

Concerning P61, the Committee felt that it could not make any decision on the scientific value of the proposed experiments on alpha-particle dynamics of rare earths until results of similar and already approved measurements on heavier elements experiment IS329) have been presented. IS329 will therefore be asked to give a status report at one of the next ISC meetings, and a decision on P61 will be deferred until that time.

Other Business

In addition to the proposals discussed above the following documents have been received:

a) ISC94-5/I10: Fabrication of implanted 7Be targets

The 3 took note of this Letter of Intent.

b) ISC/94-13 ISC/P42 Add1 and ISC/P 48 Add 1): Beam time request.

The Spokesman will be invited to make a presentation at the next meeting.

The next two ISC Meetings are on September 12/13 and December 5/6.