Targets
ISOLDE receives ~ 50 – 70 % of the protons in the complex.
RIBs are produced when 1.4 GeV protons from the PSB are transferred to the facility via the BTY line and impinge in one of the two targets.
The just-created radioactive isotopes diffuse out of the target when it is heated.
They are ionized using different mechanisms (surface, plasma, laser).
They are extracted out of the target unit that is floating at 30-60 kV.
Target Documentation to be found via: https://eam-light.web.cern.ch/ then enter #729
NORMHRS & NORMGPS from PSB. Typical target types: Uranium-Carbide-powder, Tantalum-foil, Niobium-foil, etc.
Staggered beam: STAGISO. Typical targets: Sensitive Liquid metal: Lead, Tin, etc
Work by SY/STI developing new targets and ionization mechanisms to increase the variety and purity of the RIBs. (e.g. LIST targets, RILIS new ionization schemes, molecular beams…)
The radioactive products are the ionized in one of three ways
- Surface ionization – alkali metals, elements with low ionization potential
- Plasma ionization – gases
- Laser ionization (RILIS) – 48 elements and counting! and LIST target (https://indico.cern.ch/event/1183259/contributions/5110794/attachments/2558209/4408784/Heinke_PI-LIST_final.pptx)
ISOLDE Target animation cds 2289929
Target versus convertor
1. It defines the ground potential around the separators.
2. The cage is supplied with a continuous flow of dry air to prevent sparking in the air gap and to limit the formation of nitric acid created by the passage of the high energy particles through air.
3. This volume is kept under slight under-pressure and serves as a confinement in case of accidental release of radioactivity from a target unit.
The HV supply, the isolating transformers and all target and ion source supplies are located in a dedicated room above the HRS magnets. This room is lined with sheet metal forming a Faraday cage. From here the high voltage and the target and ion source power are fed to the target areas via coaxial ducts (‘Boris tube’) which are connected to the front end Faraday cages. Thus all critical parts of the separators are enclosed in a uniform ground potential envelope.
FRONTEND 10 & 11 after LS2
Gas system upgrades after LS2
Supply of gases to the ISOLDE targets at a controlled concentration and rate is required to promote molecule formation through addition of reactive gasses, or act as a buffer gas in the FEBIAD type or plasma ion sources sources (VADIS, VADLIS, COMIC, or Helicon), where it is also used to monitor the ionization efficiency. The installation of the new GPS and HRS Frontends (FE10and FE11) at ISOLDE, gave us the opportunity to up-grade the gas supply system to the target. Both Frontends are now equipped with three gas lines which can be independently coupled to the target and ion source unit. Therefore, an upgraded ISOLDE target gas system has been designed and built (see Fig. 3, EDMS:2492542), which can be controlled remotely and it will be ready to feed these independent gas lines. The system is able to handle inert and noble gases (Ar,N2),oxidizing gases (NF3,O2) as well as other gases suchasSF6,CF4,Air, andH2(2% in argon). The pressure inside the gas system ranges from -1 bar up to 1.5 bar gauge. In parallel, an ATEX compliant gas system is under assessment to further upgrade the new gas system and allow the handling of CO in a safe manner.
The gas system features 3 different modes of operation:
• Calibrated leak operation or standard operation, where the system is filled with different gases up to a desired pressure.
• Leak valve operation, suitable for targets with no calibrated leak, which controls the gas injection in the target.
• Loop operation, used for gas purification and im-proved mixing as well as for the carbonyl metal extraction system [1].
The first gas system prototype has been success-fully built and it is currently undergoing electronic tests by BE-CEM to verify its functional specifications before installation at the GPS high voltage platform. Two additional, identical systems will be constructed for HRS and Offline 2
References
[1] Offline 2, ISOLDE’s target, laser and beams development facility S.Warren T.Giles C.M.Pequeno A.Ringvall-Moberg
[2] M. Götz, S. Götz, J.-V. Kratz, J. Ballof,Radiochim-ica Acta(2021)
[2] On-line implementation and first operation of the Laser Ion Sourceand Trap at ISOLDE/CERN D.A. Fink , S.D. Richter , K. Blaum , R. Catherall , B. Crepieux , V.N. Fedosseev , A. Gottberg , T. Kron d , B.A. Marsh , C. Mattolat , S. Raeder d,2 , R.E. Rossel , S. Rothe , F. Schwellnus , M.D. Seliverstov , M. Sjödin , T. Stora , P. Suominen , K.D.A. Wendt