Summary of the LIU-PS Meeting 106
Held on Tuesday 1st December 2015
Agenda (https://indico.cern.ch/event/459928/)
1. Approval of Minutes of Last Meeting
2. Communications
3. Follow-Up of Open actions
4. J-PARC RCS high power beam studies (F. Tamura)
5. AOB
PRESENT: K. Hanke, H. Damerau, G. Sterbini, M. Yoshii, F. Tamura, C. Ohmori, A. Blas, C. Rossi, M.
Paoluzzi, R. Steerenberg, M. Serluca, J. Vollaire, J. Jones, S. Pittet.
1. Approval of Minutes and follow-up of the previous meeting
The minutes of the last meeting were approved.
2. Communications
K. Hanke informed about the LIU Session in the next Chamonix Workshop at the end of January
(http://chamonix-2016.web.cern.ch/). K. Hanke will present an overview of the LIU-PSB and LIU-PS
projects.
A document describing the LIU project is going to be prepared and will be linked to the LIU-PS INDICO
site after the approval of the management.
The next meeting will be held on 12th January at 16h00 and will be devoted to the TT2 consolidation
activities.
Concerning the 2016 LIU-PS re-baselining, H. Damerau will contact the package holders to collect the
needed information. The latest version of LIU-PS Work breakdown structure can be found at
//cern.ch/dfs/Departments/BE/Projects/PSUpgrade/Internal/WorkBreakdownStructure/LIUWBS20160105.xlsx
K. Hanke informed about the LIU-PS abstract list for IPAC 2016. A total of 8 abstracts were presents.
The complete list can be found here.
The joint LIU-PSB and PS End-Of-Year drink will be organized on the 10th December ant 13h00 in 37R-022.
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3. Follow-Up of Open actions
There was no open action.
4. J-PARC RCS high power beam studies (F. Tamura)
F. Tamura presented the J-PARC RCS high power beam studies (Annex 1).
The Japan Proton Accelerator Research Center complex is mainly composed by a Linac ad Rapid
Cycling Synchrotron (RCS) and a Main Ring (MR).
During the 2014 the RCS underwent a major upgrade that increased the injection energy from 181 to
400 MeV and the injected peak current from 30 to 50 mA. The extraction energy is 3 GeV. This resulted
in an output beam power increased from 600 to 1000 kW.
The RCS main RF system is composed by 12 magnet alloy cavities providing a maximum RF voltage of
440 kV.
In order to mitigate the space charge effect at the injection, transverse and longitudinal painting is
performed.
In order to compensate the beam loading J-PARC RCS employs RF feed-forward method for multiharmonic beam loading compensation. A commissioning methodology was established for even and
the harmonics.
The first trial to accelerated the 1 MW beam failed and only 773 kW could be reached. The 1-MW beam
acceleration was not reached due to the over current of the anode power supply of the RF system.
By moving a convenient detuning of the RF cavity (from 1.7 to 2.1 MHz) the peak power requested
could be lowered and the 1 MW beam power could be successfully reached.
Unfortunately the beam losses around the machine pointed out to the formation of longitudinal halo.
Simulation showed that coupled-bunch motion was excited with the 2.1 MHz frequency.
A. Blas asked if the observed odd frequency components in the cavity voltage monitor were referred
to the RF of the revolution frequency. F. Tamura answered that they are referred to the revolution
frequency.
During the summer shutdown, the power converter of the RF system underwent a major upgrade to
cope with the 1 MW beam power maintaining the 1.7 MHz.
The recent beam tests showed that the losses disappeared together with the coupled beam motion and
the odd harmonics on the cavity voltage monitor. The 1 MW beam was proved to be fully operational.
M. Paoluzzi asked about the longitudinal painting procedure. F. Tamura explained that longitudinal
painting is achieved a constant injection energy constant and by adjusting the bunch/bucket
synchronization.
H. Damerau asked about the code used in for the longitudinal painting. F. Tamura explained tat was
not a commercial code but ad hoc developed code.
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H. Damerau asked if an operation with two families of RF cavities (one family at 1.7 and the other at
2.1 MHz) could be envisaged. F. Tamura commented that for practical reason all of them are operated
at the same frequency.
M. Paoluzzi asked how the cavities are tuned. F. Tamura commented that the tuning is done with a
capacitor.
A. Blas asked about the ration between the energy in the cavity for the unloaded structure and the one
of the induced by the beam. F. Tamura answered that the energy ratio is close to one.
5. AOB
C. Rossi asked to modify the amplifier of the cavity 11 (C11) to test the prototype of the new amplifier.
R. Steerenberg commented that the C11 will not be a hot spare anymore. C. Rossi observed that for
testing the new setup with the beam there is no other solution but that in case of problem a 1 h
intervention can revert the configuration to the original one. All the infrastructures are already in
places (cooling). After discussion no objection on the C11 modification was raised.
C. Rossi asked if an ECR is needed for the modification. After discussion, it was decided to modified the
already existing ECR and to restart the PS after the end-of-the-year stop with the prototype of the new
amplifier in the C11.
Next Meeting: Tuesday 12st January
Minutes reported by G. Sterbini the 5th January
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