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

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- 1 -CERN/INTC 2001-039INTC1022 December 2001ISOLDE AND NEUTRON TIME-OF-FLIGHTEXPERIMENTS COMMITTEEMinutes of the tenth meetingon November 26th 2001OPEN SESSIONThe Chairman opened the meeting by briefly mentioning the recent LHC cost-to-completion review, showing a sizable budget shortfall. He evoked the possible implicationsfor the INTC community and underlined that the success of LHC was important foreveryone.On the other hand, he pointed out that the activities of the ISOLDE and nTOF communitieswould be very beneficial to CERN by participating to keep it as a science producing placeuntil the start of LHC. In that respect the current situation appeared especially favourablewith the successful start of REX-ISOLDE and the final commissioning of nTOF wellunderway. He then reported on the ongoing audit of the ISOLDE Solid State Physicsprogramme and emphasized its theinterest for CERN in demonstrating the contribution ofthis specific community and the significance of its research within the general field ofSolid State Physics.The ISOLDE technical Coordinator, Mats Lindroos, reported on recent events related tothe ISOLDE facility. The replacement front-end, having been rapidly constructed to renderthe GPS operational again, had been completed and commissioned, somewhat behindschedule but in time to permit several runs in 2001. However, in the preparation phase ofthe first physics run on the recommissioned GPS, a time-delayed shortcut had beenencountered, prohibiting applying high voltage. This was later concluded to have beenprovoked by a considerable amount of oil inside the front-end, which stemmed from thetarget unit. The thus necessary cleaning and repair actions prohibited the use of the GPSuntil the shut-down. He then turned to reporting on the ISOLDE consolidation project. Anemittance meter device had been delivered which will permit characterization of target-ionsource units, and the entrance porch of the ISOLDE experimental hall was nearingcompletion. Furthermore, progress on target and ion sources techniques were reported on.In the upcoming shutdown period, a major renovation of the ISOLDE control system andpower supply will bring the facility on par with the hardware used elsewhere within the PScomplex.Thomas Nilsson, the ISOLDE scientific Coordinator, informed the Committee about theoperation during 2001. The technical problems with the GPS meant that most runs hadbeen rescheduled to use the HRS, with the severe limitation that the latter lacked relevantinfrastructure for collections. The grave impact of this fact on the possibilities for the Solid- 2 -State Physics and Life Sciences communities was reiterated. However, the number ofradioactive beam shifts delivered so far to approved experiments, developments and testswas 325, with a prevision of having delivered 340 shifts by the shutdown. The envisagedsavings within the CERN budget was also to affect the operational period of 2002, with ashortened period of operation of the PS complex. To partly circumvent the negative effectson the ISOLDE scientific programme, an improved operation efficiency to be achieved byfurther parallel use of the two separators and increased usage of the target units wasoutlined. For the experiments, these constraints will translate into a pronounced decrease ofthe flexibility of the scheduling process. He then continued to show a large number ofscientific and technical results obtained in experiments performed during 2001 where theoutstanding example was the successful first post acceleration of a radioactive beam, 26Na,in REX-ISOLDE made on Nov. 30th. Finally, the experiences of the pilot phase of websubmission of proposals and letters-of-intention decided upon in the eighth meeting wererecounted. The INTC community had in general reacted positively to this proceduralchange.A. Ferrari then presented a technical report on nTOF, presenting the work on backgroundreduction. After the status report presented in the ninth meeting, a working group had beenset up under the leadership of the SL/EET group to address the background problem. Asimulation of the whole facility had been made, confirming the hypothesis that the maincomponent of the neutron background stemmed from capture reactions of muons fromdecaying pions originating from the spallation target. Furthermore, tests with a massivebeam stopper had shown that ~90% of the background was not related to the neutron beam.A provisional iron shielding wall, in which gaps had to be left unfilled, had then been setup within the nTOF tunnel in order to stop these muons. The presence of this wallproduced a reduction of the background by one order of magnitude, now rendering thebeam-related background important. An amelioration of this iron shielding was foreseenfor the upcoming shutdown. Finally, first ideas for a second experimental station upstreamfrom the existing station were briefly evoked. This would permit fission studies to be donein parallel with capture experiments.The following proposals were then presented:1. Semiconductor Spectroscopy with Short Lived Isotopes; INTC 2001-033/P146;M. Deicher.2. High Accuracy Mass Measurement of the very short-lived Halo Nuclide 11Li;INTC 2001-034/P147; D. Lunney.CLOSED SESSIONPresent: J. yst, C. Dtraz*, H. Flocard (Chairman), M. Hauschild, K.-H. Langanke,K.-P. Lieb, M. Lindroos, E. Migneco, T. Nilsson (Secretary), C. Rossi-Alvarez,J.-P. Riunaud, D. Schinzel, W. Scobel, J. Suhonen, D. WarnerApologies: J.-P. Duraud, H.-J. Kluge, H. Ravn, B. Rubio* part-time- 3 -1. INTRODUCTIONThe Chairman opened the session by considering the minutes of the ninth meeting.These were approved with the following changes in the paragraph on P-138 Add. 1:The title should read ÒInvestigation of astrophysically relevant neutron-rich argonnuclei” and in the text, “spokesperson of P134” should be “spokesperson of P138”.2. Subsequently, a discussion on the delivered scientific and technical reportsfollowed:2.1 ISOLDE Technical reportIn relation to the encountered problems related to the GPS front-end, the Committeeexpressed its appreciation of the efforts done and encouraged the technical team tocontinue efforts to make the GPS available. The Committee was very satisfied thatthe good performance of the HRS had permitted a productive year. Concerns wereexpressed regarding the possible situation that the GPS front-end would not beavailable for the beginning of the 2002 running period. This was consideredimprobable. However, the precarious situation of having no available spare front-end unit was pointed out once more.2.2 ISOLDE Scientific reportThe Committee took note of the performance of the facility during 2001. Related tothe previsions for the 2002 running period, it supported measures aimed atincreasing the efficiency to compensate for the shorter operational period andanticipated that the user community should understand and show appropriateflexibility in the current situation. Regarding the reported experimental progress, theCommittee estimated that the scientific productivity had been satisfying. It alsoexpressed great satisfaction that REX-ISOLDE had commenced acceleratingradioactive beam, acknowledged this major step and congratulated the communityinvolved in the project. The electronic submission procedure was considered asfunctioning. However an interim period where INTC members will continuereceiving paper copies of proposals still appears useful.2.3 Technical report on nTOFThe Committee found that the background problem had been addressedsystematically with simulations, experiments and shielding measures and expressedsatisfaction with the results obtained by the SL/EET group with the help of thecollaboration on the experimental aspects. It was pointed out that the reported testslend confidence to the predictive power of the simulations. The Committee askedthat further simulations be performed with the final shielding configuration to assessthe impact on the experimental programme, for appraisal in the coming INTCmeeting. The experiments nTOF3 and nTOF4 (whose approval by the ResearchBoard is still pending in the absence of nominated spokespersons) were requestedto re-evaluate their capacity to reach their physics goals in the light of theperformance of the facility presently expectable for 2002. Furthermore, attentionwas drawn to the fact that the displayed experimental data did not comprise flighttimes corresponding to neutrons with energies above a few MeV and concerns wereraised regarding a possible remaining negative influence of the background in this- 4 -energy range. In view of the neutron fluence measurements envisaged at thesehigher energies, a clarification on the capability was asked. In particular the INTCrequested that this point be investigated in relation to P145 and reminded thecollaboration that a further evaluation of this proposal was dependent on answeringthe questions asked after the September INTC meeting.In the ensuing discussion, the SPS/PS Coordinator M. Hauschild briefly presentedthe previsions regarding protons for nTOF in 2002. The current schedule wouldpermit the delivery to nTOF of an integrated number of protons amounting up to7.07 1018. The collaboration is thus requested to present plans for operation in 2002taking this figure into account, as well as the PS schedule.3. DISCUSSION ON NEW PROPOSALS AND LETTERS OF INTENTThe presentations of new proposals made during the open meeting, and two lettersof Intent were then discussed.3.1 P146 (CERN/INTC 2001-033): Semiconductor Spectroscopy with ShortLived IsotopesThe scientific value of this broad experimental programme was acknowledged assuch, addressing timely questions within semiconductor physics, and the methodsproposed were seen as a unique way to fully exploit the potential of radioactivetracers available at ISOLDE. A discussion followed on the infrastructural resourcesrequested in the proposal, a laboratory space for off-line experiment with short-livedradioactive probes, preferably within the future perimeter of the radioactive "ClassC" area around the ISOLDE experimental hall. The proponents already requestedsuch a laboratory several years ago and plans for its realization have been workedout. However, the financing remained unclear to the Committee, and the involvedparties should discuss and elaborate possible solutions before the proposal ispresented to the Research Board. With this reservation, the full allocation of 40shifts was recommended for approval.3.2 P147 (CERN/INTC 2001-034): High Accuracy Mass Measurement of thevery short-lived Halo Nuclide 11LiThe proposed high precision measurement of the mass of the halo nucleus 11Li wasseen as scientifically highly interesting in view of the general interest focused onthis original nucleus. Its precise impact on theoretical models is still difficult toassess due to the present state of these models. The experiment appeared well suitedto the MISTRAL apparatus and ISOLDE. Therefore, an allocation of 12 shifts willbe recommended to the Research Board.3.3 I-039 (CERN/INTC 2001-022): Production of a 7Be sample for neutron-induced cross-section measurementsEven with the additional arguments furnished by the recent letter sent by thespokesman, the Committee was not convinced, based on the references given, thatthe scientific impact of the proposed measurements would be significant. Thus, evenin the light of the diminutive resources required for this off-line test experiment, theCommittee sees no reason to change its earlier decision not to support this Letter ofIntent.- 5 -3.4 I-040 (CERN/INTC 2001 032): Lifetime and gJ  factor measurementson 226 Ra+The Letter-of ÐIntention addresses experiments on parity non-conservation using Rathat could eventually complement high-energy searches for physics beyond theStandard Model. However, the interpretation needs a good knowledge of the atomicwavefunctions. The Letter of Intent aims at testing the limitations of atomic modelcalculations and was very positively received by the Committee.4. OTHER BUSINESSThe Chairman recalled the ongoing Audit procedure of the solid state physicsactivities pursued at ISOLDE that should lead to a document to be reviewed in theFebruary meeting. The research groups concerned with the Solid State Physics Audithad produced draft documents related to their activities. A discussion regarding thecontinued auditing process followed.The next meeting is on Monday February 25, and the deadline for submission ofproposals is Friday, January 18, 2002.The dates of the INTC meetings in 2002 are:13-14 May23-24 September25-26 NovemberThomas NilssonTel: 73809 Ð75828 (Mobile 160985)Thomas.Nilsson@cern.chINTC Secretariat: Monique Budel (Bldg 14/4-022; tel. 76 74270Monique.Budel@cern.ch

Minutes of the tenth meeting on November 26th 2001

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