Chairman: Maria J. Borge
Scientific secretary: Thierry Stora
Participants : Y. Blumenfeld, M. J. Borge, P. Delahaye (by phone), V. Fedosseev (point 3), G.J. Focker (point 5), T. Giles (point5), M. Kowalska, R. Losito, T. Stora, P. Van Duppen, J. Vollaire, D. Voulot ( point 4)
Excused: K. Blaum, J. Billowes, K. Riisager
Absent : A. Andrighetto
Presentations are uploaded there.
1. Introduction by Chairman and agenda (MJB)
MJ Borge, as new chairman of the SGUI, opened the meeting. She expressed her great thanks in the name of the ISOLDE Collaboration for the support provided to the facility by the technical teams in 2012. This was particularly important since no new data can be collected by active experiments during the 17 months long LS1. About 50 different experiments took data, of which about 95% were successful. It was impressive to see how the technical teams were oriented towards reaching the objectives of getting successful physics results from the facility; MJ Borge expresses further the wish that such a mind-set prevails for the restart in 2014.
Membership:
The agenda was amended to trigger discussions on the future membership of the SGUI. T. Stora informs the Group that P. Buttler resigned after having stepped down from the INTC chair. M. Borge informs that the ISCC chair Y. Blumenfeld is welcomed as an ex-officio member. M. Borge also informs that J. Billowes is not anymore member of the ISCC. J. Billowes will be approached to ask if he is willing to continue his mandate as member of the SGUI. The discussion went on as whether a limited duration term should be introduced for the external members. It was decided to keep the terms indefinite, and elect new members when it is necessary.
2. Past beam developments, new priorities, and TISD activities during LS1 (MK, TS)
T. Stora reports on the past Target and Ion Source Developments (TISD) activities. From the past SGUI meeting, the following beam developments had received the highest priority: 57Co, 9C, 142Sm, a new neutron converter, a Pb/Bi loop target for EURISOL, 37K, 118Te, 144Ba.
The foreseen unit to produce 57Co with reduced 57Fe impurities ZrO2-VD5 was mistuned at start-up and could not be tested with proton beam. The back-up unit Y2O3-VD5 displayed a x10 reduction of impurity, not enough to meet the requirements.
The CaO-Helicon v2.0 unit for 9C beam production as CO+ was operated on GPS with a faulty extraction electrode movement. The target unit was left at atmosphere for one hour before being coupled to the Front End and pumped down. Despite a few other delays, the unit could be operated and the source displayed stable conditions of ignition and operation. Improvements were seen on some of the Carbon isotopes such as 10C and 15C, however the release rates were slow, and 9C could not be observed, either due to a degradation of the target material or inappropriate gas phase conditions for COx molecule formation.
A new neutron converter geometry combined with a UCx target and bulk Re surface ion source has been prototyped and tested. Cs, Rb, Ga, In and Zn fission products were measured. The Zn:Rb ratios for A>80 were better than expected, of a 200-fold increase instead of 20 predicted by Monte-Carlo simulations (R. Luis et al, EPJ-A 2012).
The Pb/Bi loop target project LIEBE, a collaboration between 6 institutes, has started and will be ongoing for another 3 years.
The activity related to 37K beam development has started. First materials based on porous sintered TiO2 and TiC nanopowders were synthesized. Initial isotope release studies have been performed to benchmark the new materials with respect to the classical metallic Ti foil target used until now.
In addition, two important developments took place under IS509 and IS540 experiments: the operation of a molten NaF salt target and of a nanopowder-based UCx target for the ActILab JRA2 in FP7-ENSAR. The parameters recorded during the successful operation of a static NaF-LiF eutectic target were used to validate a concept of a high power molten salt loop target to produce p.mA of 18Ne+ beams for the b-beams. In the case of the nanopowder-based UCx, despite many difficulties encountered during the online tests, with unstable transmission through the RFQ-Cooler and beam deflection to the tape station, the nano-UCx-Re surface ion source unit displayed improved and constant yields of 11Be delivered to experiments. It seemed to keep also good yields of 30Na throughout its operation, and showed increased yields of neutron rich Cs yields up to 146Cs. It is worth mentioning here that about 2.5x less Uranium quantities was used in that unit with respect to a standard UCx batch.
Amongst some additional developments not foreseen in the list, a VADIS ion source was coupled to a molten Sn target, and displayed high intensities of 111mCd beams.
A Table of active IS experiments requiring beam developments was then shown. They consequently join the priority-1 list of beam developments for approved experiments, if they had not been included beforehand:
9C (IS445), 56,57Co (IS450, IS492, IS501), 211m,212mPo (IS456), 207-210Hg&208-214Tl (IS463), 31Ar (IS476), 77Br (IS487, IS492), 70Kr, 46-48Ar (IS490), 118Te (IS516), 140,141Pr (IS517), 221-223At, 202-205Au (IS518), 144Ba (IS523), 37K (IS527), 76-79Cu (IS535). 113-118Ba (IS545).
Discussions went on defining a new list of priorities for beam developments in 2013. Because of LS1, only offline activities and online tests at other facilities can take place. With the present team, the following list of developments will be ongoing: 8B, 9C, 37K, the LIEBE project, the nano-UCx within ActILab-ENSAR, the refractory molecular beams combined with RILIS, the new neutron converter geometry in collaboration with ISAC-TRIUMF and the Ba beams.
3. Review of RILIS developments and activities during LS1 (V. Fedosseev)
V. Fedosseev reported on the developments and activities of RILIS for LS1. He first reminded the past upgrade activities during which the copper vapour laser was changed into a Nd:YAG laser, 3 new dye lasers were acquired, together with a system of 2 pump lasers and 3 Ti:Sa lasers which can independently work in parallel. These lasers can be used with independent ionization schemes, operating in a sequential manner in which the second system takes over from the first one with minimum setting up time, or where the two systems can eventually be combined to ionize elements with mixed schemes. As a consequence, the new lasers system can cover all required wavelengths from UV to IR in the 205-940 nm range with 100mW to 20W power. 13 different elements, for more than 3000 hours of operation were provided to physics experiments in 2012 at ISOLDE. Examples of ionization schemes for Ni, Ca, Mg, Po, Au and At were presented. The highlights were ionization with narrow band laser excitation and the operation of a LIST source combined with UCx target to ionize Po beams and suppress Fr contaminants.
Valentin went on presenting the foreseen activities for LS1, namely extension of the laser cabin, the installation of a dedicated high power Nd:YVO laser for non-resonant ionization, a machine protection system which together with the laser beam stabilization and monitoring system could allow to replace the shift mode of RILIS operation by the on-call operation mode. The uprade of the laser window on HRS is to be considered in order to cope with high power laser beams and to simplify the procedure of windows replacement. The spectroscopy branch of RILIS development includes installation of a reference cell at RILIS, an improved motorization of the narrow band TiSa laser, activities to develop the ionization of refractory elements, and improvements of the ionization scheme for elements requested by the physics program. In the list of the requests, the following elements have been defined: Ba, Cr, Te and Er.
A possibility to improve the ionisation efficiency of Li by applying RILIS has been discussed. The laser ionization scheme of Li is known, its efficiency could be measured off-line and compared with the surface ionization.
A layout of possible laser installation at the new off-line mass separator has been presented. A permanent availability of such installation would enable direct testing of new ionization schemes and conduct R&D on new approaches to laser ion sources and laser-ion interaction in the RF-cooler.
4. 2 GeV BTY line upgrade (Didier Voulot for KH)
D. Voulot reported on the possible BTY line upgrade to 2GeV. The assumptions are that the beam optics and geometry in the BTY line remain unchanged, the 1.2s repetition rate is conserved, the option at 1GeV beam energy is dropped and only 1.4 and 2.0 GeV would be maintained, that the BT and BTM lines upgrade are already included in the LIU project and that the target area upgrade is included in the HIE-Design Study. There are 3 sets of magnets considered in the pre-study, the dipoles, quadrupoles, and corrector magnets. The corrector magnets are compatible with 2GeV operation. Presently the power converters are operated in cw mode but are designed to operate in ppm mode. This would relax the stress on electrical power and cooling required for operating at 2GeV, with the provision that the field stability is appropriate. With the present scheme, a replacement of 7 power converters is required, for a total of 1.1 MCHF. For the dipole magnets, a different strategy is required, namely to replace the dipole magnets with new designs compatible with the present power converters. The new design needs more space in the beam lines and requires a proper integration and investigation if the space for access in the zone is enough. The full cost for the replacement of the 4 dipoles and the manufacturing of a spare is estimated at 1.7 MCHF. Other issues such as a proper cabling, radiation protection issues upon increase of the proton beam power, have not yet been investigated in details; they are not identified as technical- or cost- show stoppers. The project is not yet approved and should be discussed at a forthcoming IEFC meeting. R. Losito said that IEFC is a required step for triggering the discussion with CERN management. He also reminded that the dumps behind the ISOLDE target stations are not compatible with 2GeV, 12kW operation, and their replacement should not be forgotten when estimating the total cost of this project. Thus at present an estimation of 2.8MCHF with 20% contingency is foreseen for the items investigated so far, with aspects related to cabling, vacuum, dumps, left out of the estimation. A significant cost related to the upgrade of the ISOLDE beam dumps to 2GeV, ~12 kW, is to be provisioned.
5. Isolde infrastructures during LS1 (ISCOOL, tape station, Faraday cups) and start-up in 2014 (RC, T. Giles, G.-J. Focker)
5.1.- T. Giles presented the foreseen plans for the renovation of the RFQ Cooler, especially to correct for the misalignment detected during operation. Its transport to the class A laboratory is foreseen for the coming days, where its level of contamination and regions of misalignments will be assessed. M. Borge and M. Kowalska asked about the problems of beam instabilities and sparks that were experienced during operation in 2012. T. Giles said that those will also be addressed by replacing the cables and connections, including the faulty ones that were at the origin of the problems. Since it was difficult to diagnose the origin of the problem, some monitoring tools should be foreseen in a new device. Finally the He gas injection system will also be renovated. A part of HIE-DS, a second RFQ cooler is being designed and assembled for test on a dedicated offline separator. It will be made compatible with the ISOLDE beam line layout. In this way it can become a spare for the existing equipment in case of severe failure.
Tim then reported on the present status of the fast tape station. He reported on the drawbacks of the present design, namely rotating feedthroughs that developed gas leaks, problem of spare parts, defaults leading to tape rupture, likely originating from the high mechanical stress from the motors on the tape. The documentation lacks many details. Finally the detectors have energy dependant efficiencies, and suffer from high background levels. With such a high number of items to be improved, it is proposed to start making a new design. It should bring together simplicity, robustness and flexibility. It was proposed to organize a one day workshop in about a month to trigger some exchange of information with external experts. Synergies with the ongoing project and involved people of the ISOLDE decay station will also be sought after (an initial kick-off meeting was organized on 3rd October 2012).
5.2.- G. J. Focker went on presenting activities foreseen for the consolidation of beam instrumentation at ISOLDE. On the front of Faraday cups, GPS.FC20 appears to be stuck. Access and repair will take place benefiting from the radioactive cool down to access the Front-End 7 Faraday cage. GPS.FC490, HRS.FC490 and GPS.FC300 are based on a similar design with some adaptations. This had caused issues during interventions this year. The strategy is to order a common spare and the different pieces for adaptation to allow for a spare unit to be available within an hour. The new pico-ampere-meters (PAM) were seen to be sensitive to single event upset in the separator magnet rooms. They were moved out, but the need for long cables had decreased the performance of the devices. The design should evolve to physically decouple the amplifiers, that should not be sensitive to the radiation level, and bring them back to their former position, while keeping the rest of the electronic card outside of the rooms. The rest of the 25mm Faraday Cups and scanners have or will have spares, a list being set up to make sure that enough stock is available for the start up in 2014.
Gerrit Jan went on, drawing the attention of the Upgrade Group that some REX diagnostics are unique devices with little or no documentation available. For instance one of the two collector plates is broken. It will be removed and a new documented design with standard pieces will be made. A new design of the electronic card of the scanners has been started, and is so far on halt because of other priorities. Specifically discussions on other types of scanners, such as Alison scanners, should take place in a separate meeting. Finally the Grids of the linac are becoming obsolete, and decision should be made to make some spares or evolve the design for a new set of devices, for instance sharing common features with the new SEM-Grid of the PS Complex. As a conclusion, BE-BI is aware of the issues related to lack of available spares for ISOLDE BI devices. This is followed up and properly addressed for the start-up in 2014.
6. AOB
MJ Borge enquires about the possibility to anticipate the production of the target units for 2014. T. Stora answers that until now the production of target units is discussed two or three times per year, a weekly meeting with M. Kowalska anticipates the requirements and possible changes, and that for the first time in 2012 the units were due to be ready one week ahead of their operation. While in principle some production could already be anticipated, it is somewhat difficult since the team in charge of production is busy with the work related to the required maintenance of infrastructures during the shutdown.
MJ Borge also inquires about the update of the yields database of ISOLDE. T. Stora said that it is linked to the publication of the results, which will take place with EMIS and some other publications in preparation.
7. Next meeting
The next SGUI meeting is foreseen on Tuesday morning 22nd October 2013.
Minutes by Thierry Stora