CYV, 09/08/2013
Minutes of the 59th PS Upgrade Working Group
Date: 06. August 2013
Present: Heiko Damerau, Sergio Rioja Fuentelsaz, Roland Garoby, Paolo Chiggiato,
Simone Gilardoni, Alexander Huschauer, Giovanni Iadarola, Elias Metral, Roberto
Kersevan, Serge Pittet, Giovanni Rumolo, Guido Sterbini, Mauro Taborelli, Christina
Yin Vallgren, Raymond Wasef
Meeting:
http://indico.cern.ch/conferenceDisplay.py?confId=266082
a) Progress on electron cloud monitors in the PS (Christina)
- Christina presented a summary of the current status of the electron cloud monitors
planned to be installed during LS1 in the PS.
(http://indico.cern.ch/getFile.py/access?contribId=0&resId=0&materialId=slides
&confId=266082)
- Two proposals of electron cloud monitors have been discussed at earlier PS-LIU
meetings (48 & 51) to provide predication of the EC build-up distribution in the
PS magnets for higher intensity beams in the frame of the upgrade program as
well as validation of the EC simulation models and codes. MU98 has been chosen
to have two flanges installed for the electron cloud monitors.
- The first proposal is shielded pick-up. The electrode will be introduced through a
flange of DN35 installed on the horizontal direction where the only opening of
magnet is located. The second proposal is to measure electron cloud signal via
electron-photon-emission through an optical window installed in the vacuum
chamber. The details of the two proposals and implementation drawings can be
found in the presentation.
- A new experimental set-up has been built for the electron-photon detection to
study the inverse-photoemission yield on stainless steel, main material for the PS
vacuum chamber. Several difficulties have been mentioned during the talk and
more investigation is ongoing. However, the situation for the photon detection in
the PS would possibly be different because no electron gun is present and we can
probably directly select a certain/narrower wavelength region for studies by using
optical filters.
- After the meeting, a good suggestion came from Heiko on measuring the residual
light level in the PS beam pipe during LS1 to check the background level.
b) Electron cloud simulations of PS chambers (Sergio)
- Sergio presented a summary for electron cloud simulation dedicated to the PS
chambers:
(http://indico.cern.ch/getFile.py/access?contribId=1&resId=1&materialId=slides
&confId=266082)
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The total length of the PS is 628m and 78.6% of the PS consists of 100 combined
function magnets. 68 of the 100 magnets contain standard vacuum chambers.
Lists of different PS chambers have been shown during the presentation.
The e-cloud thresholds depend on several parameters: Pattern train, chamber
shape and magnetic field. The simulation has been performed on Chamber ST (4
magnets R,S,T,U), Chamber ST (drift section, SS98) and chamber
SP.INT.(focusing part of T & U MU57) – details of the chambers were mentioned
during the talk. Only the last 6 ms of the cycle before the ejection has been taken
into account in the simulations.
Energy loss per meter due to e-cloud has been estimated. For the simulations of
stable phase shift, the worst scenario is taken into account. Because when a
magnetic field is present, the multipacting thresholds are higher and then the ecloud signal gets lower. A downward prediction is used for the phase stable shift.
Except for an intensity of 1.0e+11ppb we would see a stable phase shift around
0.5 degrees for the last 380 microseconds of the cycle. But this was a downward
prediction because the whole machine was assumed to be made of main magnets
(only one field was taken into account) and there is more e-cloud expected in the
drift sections.
The future work for the stable phase shift will consider the real accelerator with 4
magnetic fields, straight sections as well 4 kinds of vacuum chambers.
c) News of the PS-LIU project (Simone)
- Simone showed a list of measurements foreseen after LS1.
(http://indico.cern.ch/getFile.py/access?contribId=2&resId=0&materialId=slides
&confId=266082)
- TDR: a gentle reminder for those who haven’t sent or uploaded on the webpage,
please don’t forget.
- Budget 2013: The budget of WU concerning vacuum, control and transport has
been confirmed yet.
d) AOB
- Guido: working with Freddy on the characterization of the old amplifier for the
transverse damper in order to compare the similar measurements with the new
one.
- Alex/Raymond: working on the simulations for the space charge and a
presentation on this topic can be given in one month’s time.
- Heiko: preparing for the Oct review as well working on the TDR. He also
mentioned that 11 cables in the same length need to be made for the 10 MHz
cavities at the moment, in total 44 cables are needed.
- Roland: asked about when the review for the PS-LIU will take place. Simone
plans to have the review for the PS-LIU in fall, 2014 (after the restart of the
machines).
- Paolo: mentioned about the delay of MU57.
Next meeting: 27/08/2013, 15h30, 865-1-D17
Minutes by Christina Yin Vallgren