CERN. Geneva. ISOLDE and Neutron Time-of-Flight Experiments Committee

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CERN/INTC 2000-019INTC 310 March 2000ISOLDE AND NEUTRON TIME-OF-FLIGHTEXPERIMENTS COMMITTEE (INTC)Minutes of the third meeting onMonday 28th February 2000OPEN SESSIONAfter a few words of welcome the Chairman asked M. Lindroos, the PS division TechnicalCoordinator now responsible for ISOLDE to describe the organisation and responsibilities of thePS-ISOLDE team.  M. Lindroos explained that ISOLDE operations will, from 1 April 2000, beintegrated into the structure of the PS "expert groups", which are concerned with the variousfacilities operated by the division. The PS-ISOLDE group will from that date take care of theoperation of the ISOLDE facility, ensure its long-term future, participate in the development ofnew radioactive beams and provide technical support for ISOLDE users. To these ends, thegeneral PS personnel and workshop resources will be made available when necessary.Thomas Nilsson the ISOLDE coordinator, presented a brief summary of the 1999performance and the proposed 2000 schedule. In 1999 195 radioactive ion shifts had beendelivered with very stable GPS and proton beam operation. Of 36 experiments with a totalrequest of 401 shifts, 19 were fully and 15 partially scheduled. In 2000, with 52 experimentsrequesting a total of 572 shifts, it is expected that 390 shifts will be delivered, of which100 should be with the high resolution separator (HRS).H. Ravn then presented a short report on the HRS, recalling its historical origins at the timeof the old SC-ISOLDE, its progress to date at the PSB-ISOLDE, the remaining technicalchallenges to be solved, and its performance characteristics at the expected startup date inMay 2000.The Chairman then invited E. Radermacher to present the Neutron TOF Facility TechnicalDesign Report (PS213). This was described under the general headings of the PS beam, the leadtarget zone and the 200 m flight tube. Simulation studies of neutron fluxes and of charged andelectromagnetic backgrounds and radiation doses at various locations were also described, andthe expected installation schedule was outlined.Presentations were then made of the following proposals and progress reports:P123: Determination of the neutron fluence, the beam characteristics, and the backgrounds at theCERN-PS TOF Facility.P115: Diffusion Mechanisms and Lattice Locations of Thermal-Equilibrium Defects in Si-GeAlloys.P116: Isospin mixing in N » Z  Nuclei.P117: Investigation of the impact of the 39Ar(n, a )36S reaction on the nucleosynthesis of the rareisotope 36S.P85 Add. 1: Investigations of Deep-Level Fe-centres in Si by Mössbauer Spectroscopy.P119: Laser Spectroscopy Studies in the Neutron-Rich Sn Region.P121: Precision study of the beta decay of 74Rb.P64 Add. 3: Test of a high power target.2CLOSED SESSIONPresent  :  B.W. Allardyce, J. Aystö, G. Bauer (invited), C. Détraz, J.-P. Delahaye,J-P. Duraud, J. Eades (Secretary), H. Flocard (Chairman), P. Van Isacker,K-L. Kratz, M. Lindroos, E. Migneco, T. Nilsson, H. Ravn, C. Rossi-Alvares,J-P. Riunaud, B. Rubio, W. Scobel, R. Voss (for G. Goggi), P. Walker.Apologies   : W. David, K.P. Lieb.H. Flocard first welcomed the new ex-officio members of the INTC, J.-P. Delahaye (newleader of PS division), J.-P. Riunaud (who will represent PS division in future at the INTCCommittee's meetings) and M. Lindroos, the PS technical coordinator of ISOLDE. H. Ravn willremain in the Committee for his invaluable expertise in the domain of targets and the generalscientific life of ISOLDE. The Chairman also introduced G. Bauer of PSI, who has been invitedto evaluate the Technical Design Report of the nTOF facility.The minutes of the third meeting were then approved without change.The Committee thanked H. Ravn and T. Nilsson for the technical report on the HRS andon the ISOLDE performance and schedule for 2000, respectively. It was noted that the HRS isexpected to function initially in low-resolution mode.The first item for discussion in the closed meeting was the nTOF Technical Design Report(TDR). In presenting his evaluation of this, G. Bauer reported that while the scientific case forthe nTOF facility was well documented, several questions and points of criticism could be raisedconcerning the TDR itself. These included the basic conflict between optimising the nTOF designsimultaneously for both the epithermal and high energy neutron energy regions, an apparentoverestimation of the neutron source strength, the risk of burning out the lead target by a singleproton bunch, and some questions about the use of water as the target coolant. The Committeetherefore asked G. Bauer to summarise his evaluation in the form of a complete written list ofquestions to which the nTOF community is invited to reply. It may then be asked to prepare arevised version of the TDR.The Committee then concluded its review of the 700-shift backlog in the ISOLDEprogramme begun in the second INTC meeting of 29 November 1999. After discussing thereplies to the questionnaire sent after the last INTC meeting, it was decided to cancel theoutstanding shifts of the first class of experiments (those recommended before 1996). A letterwill be sent to each spokesman to this effect, pointing out that updated proposals maynevertheless be resubmitted to the INTC. In the case of the second and third classes (experimentssubmitted before 1998 with more than 20% of their shifts outstanding, and Tests and LOIssubmitted before 1998) it was agreed to take no further action except for IS303 (Tilted-foilpolarisation and magnetic moments of mirror nuclei at ISOLDE) and IS356 (Search for physicsbeyond the standard model via positron polarization measurements with polarized 17F.). IS303should, by the September INTC meeting provide, technical information establishing the state ofreadiness of the group and its ability to finish its outstanding shifts in 2001. In the case of IS356,the spokesman's own suggestion of reducing the number of 34 outstanding shifts to 12 (for118Sb) and a maximum of 6 (for 17F) will be followed.The closed meeting continued with a discussion of the proposals and progress reportspresented in the open session, as follows:P123: Determination of the neutron fluence, the beam characteristics, and the backgrounds at theCERN-PS TOF Facility.The proposal represents a good description of an overall experimental project to check thegeneral performance of the nTOF facility, and the experimental techniques associated with eachaspect were considered adequate. The proposed measurements clearly represent a largeinvestment of time and effort and it was felt that the details of these studies as well as theirplanning and implementation will need to be treated in greater depth than is the case in the present3proposal. The Committee will therefore recommend that the Research Board allocate therequested 7 weeks of test beam, and will also require the collaboration to make a better focuseddescription of the planned programme of tests.P115: Diffusion Mechanisms and Lattice Locations of Thermal-Equilibrium Defects in Si-GeAlloys.This was considered to be an interesting and worthwhile experiment in spite of thedifficulty of obtaining dislocation-free alloys. The Committee therefore recommends that therequested 12 shifts be allocated.P116: Isospin mixing in N » Z  Nuclei.The experiment has interesting repercussions for the standard model and the Committeerecommends an initial allocation of 10 shifts for the Cu and As experiments with the first (Nb)target. This should be followed by a progress report and a new request.P117: Investigation of the impact of the 39Ar(n, a )36S reaction on the nucleosynthesis of therare isotope 36S.While 36Ar is not of a primary importance in today's nucleosynthesis scenarios, this smallexperiment aimed at producing a target to be used in the ILL reactor, was considered worthwhileand the 6-shift request will be recommended to the Research Board.P85 Add 1: Investigations of Deep-Level Fe-centres in Si by Mössbauer Spectroscopy.It was considered that the proposed investigations of deep level Fe centres in Si were not ofsufficient importance to warrant the requested allocation of shifts. Moreover, the Committee feltthat insufficient explanation had been given on why the temperature dependence analysisdescribed in the proposal could answer questions on the nature of the additional spectroscopicline.P119: Laser Spectroscopy Studies in the Neutron-Rich Sn Region.The group already has a good record and the physics motivation of the proposal was clearlypresented. However, it was somewhat unclear as to where the boundary lies between test shiftsand experimental ones. For this reason it was decided to recommend initially 12 shifts for thetests, and to ask the group to present an Addendum on the results of these before the Committeeagrees to allocate beamtime for the experimental work.P121: Precision study of the beta decay of 74Rb.The precision studies of the beta decay of 74Rb were thought to be interesting. For themoment a 23 shift allocation will be recommended to the Research Board. According to the thegroup's own estimate this will suffice to demonstrate the capacity i) of MISTRAL to significantlyreduce the error bar of 74Rb (11 shifts) and ii) of ISOLTRAP to reach an accuracy of 10 keV onthe mass of 74Kr (3 shifts). The remaining allocation (9 shifts) corresponds to the correlatedanalysis of the spectroscopy following beta decay of 74Rb. The collaboration will be expected topresent a progress report before the remaining shifts can be attributed.P64 Add 3: Test of a high power target.The value to ISOLDE of the proposed continuation of these target tests was recognized,and the full allocation of 15 further shifts will be therefore be supported.4OTHER BUSINESSThe following Proposals, Progress Reports and Letters of Intent have been received by theINTC:P118: Charge radius measurement of the halo nucleus 11LI.P91 Add 2: Further Measurements of the 7Be(p, g )8 B cross section with an implantedradioactive 7Be target and its implications for the solar-neutrino "puzzle".P122: Three-particle breakup of 12C in the beta-decay of 12B.I31: Letter of Intent: Studies of neutron-rich isotopes of bismuth, lead and thallium by means ofa pulsed release element selective method.The Committee took note of the Letter of Intent (I31) and encourages the collaboration toprepare a proposal on these lines.The presentation of Proposal P120 (Probing the structure of very neutron-rich nuclei in thesd-pf shell by combined delayed neutron and gamma spectroscopy.), initially scheduled for thepresent meeting, has been postponed until the next one at the request of the spokesperson.The next INTC meeting will be held on 15 May 2000. Please note that the Open Sessionwill exceptionnally start in the morning at 9:00 h. in the Council Chamber, followed by theClosed session in the 6th floor Conference Room, and will last all day.J. EadesINTC Secretary, Tel.76 74273John.Eades@cern.chINTC    Secretariat:  Monique Budel (Bldg. 14/4-022) Tel.76 74270Monique.Budel@cern.ch

Minutes of the third meeting on Monday 28th February 2000

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