Chairman: Yorick Blumenfeld
Scientific secretary: Thierry Stora
Present: Klaus Blaum. Yorick Blumenfeld, Maria Garcia Borge (on phone) , Peter Butler, Pierre Delahaye, Piet van Duppen, Valentin Fedosseev (for point 5), Kieran Flanagan (replacing J. Billowes), Magdalena Kowalska, Roberto Losito, Bettina Mikulec (replacing K. Hanke), Thierry Stora, Fredrik Wenander (for point 6)
Excused: Richard Catherall, Karsten Riisager, Joachim Vollaire
Presentations are uploaded there.
1. Minutes of last meeting (YB)
Upon a request from K. Blaum, some details on point 7 were further provided by Roberto Losito, on behalf of Richard Catherall:
The 1st call for tender to replace the ISOLDE robots did not attract convincing proposals. The timeline of the project has thus been revised as follows: by 1st half 2012, acquisition of a first robot demonstrator and tests. If this phase is successful, the second robot will be acquired. At present, specific training on Robot programming is provided to selected project team members.
The minutes from the last meeting were approved.
2. Developments in 2011 (TS)
The SGUI members were reminded the priorities set for beam development at the last meeting: Recovery of standard 30Na yields, successful production of 72Kr, production of 8B, completion of 142Sm beam development. In addition 9C beams, and potential of different target/VADIS ion source combination for physics needs.
The following results were reported:
Tests of a high density UC target material (part of the ActILab program, a JRA activity within the FP7-ENSAR project) were done with the UC440 target unit. The purpose of the tests was to determine if the material used in a standard ISOLDE production unit configuration would deliver improved yields of different elements. Different alkali isotope beams were assessed, and compared to reference figures (obtained with a standard UCx material) from the ISOLDE database, and to data collected at the IRIS facility at PNPI, Gatchina. Recorded yields were systematically below the ISOLDE standard yields, and thus this high density UC does not deliver improved beam intensity despite a x4 higher uranium mass loaded in the test unit vs a standard ISOLDE production unit. This high density UC material will however be very useful for additional tests and analysis, as it is well characterized in terms of phases, chemical composition, and microstructure.
140Nd beams produced with RILIS and a low work function GdB6 cavity, with a beam purity of 40-60%, were successfully delivered for IS496. Progresses for 142Sm beam production by RILIS in GdB6 have been made with the successful development of the laser ionization scheme. The previous published scheme had a misprint in one of the transition frequencies, which is the reason why no Sm beams were observed during the last TISD run. Tests in a GdB6 cavity can now proceed.
The combination of the VADIS ion source with CaO, Y2O3 and UCx targets has been assessed for potential physics needs: It is confirmed 35Ar beams with low level of 35Cl can be delivered for the WITCH experiment but requires special preparation of the production unit. Y2O3-VD5 configuration can deliver beams for Solid State Physics: 73As for emission channeling, 57Co for Mossbauer spectroscopy and 61Cu for future applications. Intensities of 48Cr, 75Se and 77Br are appropriate, however there is still too much 48Ca and CaCl (A=75, 77) stable contaminants. Further efforts to reduce both Ca and Cl contaminants are thus required. Finally the delivery of 96Kr suffers from 96Mo stable contaminants, Mo being part of the set of materials used to build the VADIS source. A fully Tantalum-based VADIS prototype has been manufactured and will be used online for IS485 this year. Results will be reported at the next SGUI meeting.
The development of 8B beams are part of the PhD thesis of C. Seiffert. He’s first acquiring some training with 9C molecular beam development. Tests with a new plasma ion source, nanostructured CaO target and modified structural materials for COx molecule compatibility will take place in 2011. Activities directly related to 8B beam development will follow up.
72Kr beams are due to be delivered later this year. It is worth mentioning a molten NaF salt target prototype under development for IS509 is expected to deliver x4-8 increased yield vs the present 2e4/muC figure.
3 additional ongoing or possible developments are reported:
The online LIST tests were done in collaboration between the TISD team, the RILIS section and Mainz University. The LIST technology was successfully operated online with the Ti442 unit for the production of Mg beams. Suppression factors for impurities of more than 1000, and drop in RILIS yields of ca x30 for Mg beams were documented.
Optimization of the ISOLDE neutron converter is ongoing in collaboration with R. Luis, ITN Lisbon. Improvements of fission yields and reduction of neutron deficient isobaric impurities for isotopes around the doubly magic 78Ni and 132Sn nuclei, such as 80,81Zn and 130,131Cd have been simulated with Fluka. In relation with point 7 in the present Agenda, this development would allow operating Ucx units directing the beam to the n-converter instead of the target with no loss of isotope beam intensity for fission fragments.
A proposal to operate online, after LS1, a high power molten Pb/Bi EURISOL target loop prototype has been presented. External institutes, such as ESS, Myrrha, CEA, have already expressed their interest in participating in the project, and are ready to contribute with in-kind and personnel resources. If this development is successful, several beams and approved INTC experiments would benefit from it, along with new beams available in the future for possible new physics proposals.
3. Priorities for target and ion source development (MK, TS)
M. Borge suggested taking actions to increase the publicity on the Target and Ion Source Development (TISD) activity. T. Stora already took the initiative to edit a regular section in the ISOLDE Newsletters. In addition, participation to large conferences in the Nuclear physics and structure community takes place, as shown for instance in the last ARIS conference.
P. van Duppen asked if some publicity for the LIST developments could be undertaken, upon which the Group responded positively
The Group decided to attribute a Priority 1 to the developments related to the neutron converter and the Pb/Bi loop prototype, because of their potential impact on accepted or possibly new physics proposals to INTC, such as IS477, IS490 or IS521.
Different beams could not be delivered this year and therefore join the Priority 1 list for Beam developments:
A=75, 77 (stable CaCl contaminant) for is453, is487, is492.
Lack of intensity on 140Pr for is517 (Collaps collaboration)
Dy for Isoltrap : yield + high contaminants
221-223At beam
Lack of intensity and/or too much contaminanat on Er, 178-180Yb, Dy beams for is 498 (Isoltrap collaboration)
Lack of intensity for 70,71Kr beams for is490 (Isoltrap collaboration)
As priority 2 developments, the following items were listed:
Lack of intensity for 118Te (for is516) and 111Sn (for is492) from CeO targets
N-rich Hf, Lu for I-85
4. PS Booster upgrade or RCS (B. Mikulec)
B. Mikulec presented the developments and present status of the PSB 2GeV Upgrade project and the RCS study. An energy upgrade of the PSB was initiated after the Chamonix 2010 workshop, documented with a feasibility report released in sept 2010 (https://edms.cern.ch/document/1082646/3). At the same time the proposal of a new RCS machine was put forward by C. Carli. The motivation to reach 2GeV energy is driven by the LHC upgrade needs, more particularly with the aim to reduce space charge limitations at PS injection. The present scenario is a 1/1.4GeV beam energy extraction for ISOLDE, and 2GeV for other beams, with identical pulse structures of 5.6 1013 proton/pulse. The project could be realized during LS1 (start May 2013, duration 20 months). Further details were given on the status of the RCS design study. The original implantation inside the PS ring is not practicable. The main difference when compared to the PSB upgrade project is a 10Hz operating frequency, a 1013 proton/pulse intensity, and a 2GeV proton beam extraction energy for all users, including ISOLDE. The present design includes a three-fold structure of ca 120m of circumference (https://edms.cern.ch/document/1154705/1.0). Decision on which option will be favored should be taken by CERN management in Fall 2011. The following requests were subsequently presented:
- to address and provide conclusions on the impact of these beam characteristics on (HIE)-ISOLDE target designs
- to provide feedback on the impact on operation and physics program if the case 1.4GeV proton energy alternative would be dropped for ISOLDE.
In the subsequent discussions, Y. Blumenfeld pointed out that 2 GeV proton energy available for ISOLDE had already been discussed with S. Bertolucci, which confirmed this variant was already integrated in thePSB-upgrade project. This seems not to be confirmed by the LIU project team, which has not yet received any specific instructions on this subject.
5. Rilis operation (V. Fedosseev)
V. Fedosseev reported on the status of the upgrade of RILIS and on operational issues. The upgrade started in 2008. By 2011, the copper vapor lasers were replaced by a diode pumped solid state Nd:YAG laser and a back-up system; new dye lasers were installed, providing better stability and extending the operational well into the UV region; finally Ti:Sa lasers were constructed and installed. Mixed ionization both with the Dye and Ti:Sa lasers were tested online this year. The present configuration provides better reliability, flexibility, and less down-time in operation.
V. Fedosseev went on reporting on the successful online tests of the LIST trap to reduce isobaric contaminants and deliver Mg beams, the development and production of Sm and At beams, which brings the total number of elements produced by RILIS to a total of 31. Today RILIS operation is driven by 4 persons on shifts (8 hr) + 1 person on call, which imposes a maximum 2500 hours of possible RILIS operation per year, with no more than 3 weeks continuous operation blocks. The implementation of a shifts-free mode of operation requires reliable machine protection/safety and performance monitoring systems. In the first category one finds protection systems against the consecutive risks associated to ethanol or water leaks, and in the second one, control and feedback loops on laser wavelengths and beam position.
6. REX operation (F. Wenander)
F. Wenander reported on the constraints related to scheduling of REX beam times. The set-up of ISOLDE and REX parts are presently done on a 1+3 days set-up time scheme. This includes the separator set-up, some characterization of the beams, injection of a pilot beam into rex-trap and rex-ebis, scaling of the linac and optimization of the breeding time. The third day is used for further optimization and general checks. In the present scheduling, the RILIS beam set-up and the yield checks are not integrated as such and must be in some sort squeezed in. Other constraining items were subsequently listed: competing for RF support due to late start-up in the year, no TE-VSC piquet, Miniball availability, operation requiring one machine specialist at any one time, beam sharing of the separator, risks related to delivering beams on Friday afternoons. Different upgrades would improve future operations: more/better diagnostics, some items being already in progress, improvement of the vacuum in the REX separator and rfq, and improvement of the operating standards of the related equipments, including proper levels of alarms and definition of written procedures. Evolution of the operation in the short term tends towards less stressed REX operation since increasing understanding on the set-up is gathered along the years, the linac has become so-to-say scalable, and beam changes could be undertaken directly by trained users for the first time this year. Additional issues to be addressed are the so-called CERN standard solutions enforced on the REX machine which turn out to be only known from a single specialist, the cathode improvement lifetime project which lacks manpower, and to make sure the HIE-ISOLDE upgrade will keep the scalability feature of the REX Linac. Finally, new information should be obtained from the forthcoming parallel operation of WITCH and REX, of an increasing number of beams scheduled this year, and of different beams delivered for several experiments.
7. Production of and operation with UCx targets (TS)
T. Stora reported on the present status of UCx target production and on limitations related to their operation. The share of UCx targets delivering beams for approved experiments has steadily increased over the past few years, to reach 72% of the scheduled physics shifts in 2010. This was produced with 12 new units, meeting the upper limit set with the present resources allocated for their production, and the re-use of 2 old ones from previous years. The present bottlenecks which prevent an increase of the total number of units per year is the time required to perform the chemical reaction to get UCx from the powder (2 weeks), the different locations where the units are assembled in our workshop and where the unit is loaded with UCx in the Class A work sector of ISOLDE (Bld 179), the requirements to have 2 people at any time for manipulations in bld 179. The present limitation of 12 units/year is therefore still enforced. Possible ways out would be to recover an offline mass separator in bld 179 for quality assessment of the units before they go online, development of a new UCx production process (under investigation by A. Gottberg within ENSAR-FP7 ActILab, the prolongation of target lifetimes, also expected from ENSAR and HIE-ISOLDE studies. K. Blaum also suggested looking for external suppliers. New information on which UCx target to use should become available in 2014, at which point an informed decision should be taken on the proper option to follow for UCx target production for the ISOLDE facility. First improvements on UCx target unit operation constraints could result in the reduction of the required radioactive cooldown period after a careful investigation of the radioactive gas releases associated to target exchange operations and optimization of the neutron converter layout of ISOLDE will be completed.
8. AOB
n.a.
9. Next meeting
2nd Feb 2012
Minutes by Thierry Stora