Minutes, Slow Extraction assisted by bend crystals in the SPS, 25 September 2015,
16:00, 866-2-D05
Present: B. Balhan, G. Cavoto, M. Fraser, F. Galluccio, Lars Jensen, S. Montesano, S.
Redaelli, W. Scandale
S. Montsano - Status of CpFM installation in TT20, ECR preparation
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Discussion in YETS planning meeting triggered the preparation of ECR, to be
written by Simone.
The exact position of CpFM is defined as upstream of QTLD.21030 where the
existing beam instrumentation area is shown in the drawings. We should take
care with referencing these drawings, as they are likely out-of-date and the
integration situation should be checked.
Lars suggested that Simone contacts Sonia Jimenez to sort out naming.
Walter pointed out that based on previous, similar devices a name like
BCPFM would be suitable. Lars also suggested a space reservation request
document is circulated, although Simone prefers to keep a single ECR
document.
ECR will be signed by Simone, but who else should be responsible. Matthew
stated that as it is a UA9 device ABT would not need to sign it but could check
it, to be discussed with Brennan.
Walter confirmed that the device is under the responsibility of UA9.
UA9 are looking for support to carry out the mechanical work once device is
received, installed and commissioned. Simone estimated the time as:
o installation/alignment: 1 day.
o mechanical tests: 1 day.
o Walter suggested 1 week as the upper limite.
Walter insisted that a CERN standard radiation monitor is installed to predict
damage to the PMT, as well as any additional dosimeter contributed from
external collaborators. Simone agreed that both will be installed.
It was stated that we do not need an impedance measurement for where this
detector will be installed outside of the ring in TT20, however, as it is a
prototype for future UA9 in-ring detectors impedance measurements are
preferred in the long-term.
F. Velotti (presented by M. Fraser) - Optics status update (follow-up of actions)
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The MST and MSE operating at nominal deflection at 270 GeV can work in DC
mode during a long coast cycle. The ABT expert (Jan or Bruno) must be
contacted before this is implemented during the MD so that cooling can be
monitored and the spark rate of the ZS surveyed.
The extraction bumpers need checking for use in DC at 270 GeV.
For the SFT optics Qx = 26.62, a single-pass of the crystal with 160 urad kick
and 13 urad scatter was simulated assuming a large diffusion rate covering
the thickness of the crystal (1 mm). This includes an extra turn in SPS before
extraction. With the crystal at 7\sigma a separation of 11 mm can be
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achieved. For slower diffusion rates and conservative diffusion rates this will
increase to closer to 17 mm.
The beam will need to be bumped 10 mm closer to the ZS than is done on the
SFTPRO cycle today.
In order to understand the beam distribution at the ZS further work is
needed in collaboration with the collimation team.
Stefano mentioned that multiple-passes/scattering effects should be
considered and this could be investigated. He encouraged Matthew and
Francesco to make contact with him next week.
Walter estimated 30% of the beam might undergo scattering. From
experience in the 90’s one could expect impact parameters of 0.1 mm and an
angular spread of 40 urad for those particles channeled. His feeling is that the
separation is adequate.
The main discussion focused on beam diagnostics and how the extracted
beam would be measured and what observables could be used to tune and
set-up the extraction.
Lars requested a wish list to be produced and some basic beam parameters in
order that he can make some conclusions on what might be measurable with
existing diagnostics. Matthew will prepare this document such that Lars can
be invited in the future to present.
Clearly, if the existing diagnostics can’t measure the low beam intensities
then there is little motivation in attempting this MD before the CpFM is
installed. Walter expects something in the range of 106 p+/s extracted.
Francesca will provide a MEDIPIX beam profile and position downstream of
crystal that can be used as input to the tracking simulation to estimate the
beam distribution at the ZS.
Matthew suggested the use of diamond detectors, which are presently being
used to monitor the quality of beam injected into LHC. The remnant
background radiation is of course an issue and an accurate placement of the
diamond in the shower created on the ZS wires would be important. To be
kept in mind.
Round table:
Verena sent an email reporting that the coast is no problem for Q26 but including
the extraction equipment has not yet been done (not ideal for safety issues).
Therefore, a new cycle is required. Verena still needs to check whether coasting the
beam into TT20 and up to the TED is possible at 270 GeV.
Bruno reported that there are a few HV cables rated up to 8 kV available in LSS2,
these are equipped with 2 signal cables.
Actions:
Simone to prepare ECR for circulation.
Matthew to provide a BI wishlist to Lars including estimated beam parameters
(intensities, beam sizes etc…)
Matthew to discuss with Brennan if ABT support for installation during YETS is
realistic.
Matthew and Francesco to analysis MEDIPIX distribution and add to MAD-X tracking
routine.
Matthew to check extraction bumper duty cycle at 270 GeV with ABT.
Lars will ask around and look into what instrumentation was used in past crystalassisted extraction experiments.
Walter to report next time on how we request additional MD time.
Lars will present at a future meeting once he has enough information to make
conclusion on what might or might not be measurable with existing diagnostics.