Minutes of the LIS Section meeting held on 9^th August 2010

Present: G. Arduini, S. Aumon, H. Bartosik, C. Carli, M. Chanel, L. Fievet, P. Jackson, B. Mikulec, M. Newman, G. Prior

General Information (Gianluigi) 

Gianluigi reminded the machine coordinators to distribute the weekly report on the status of the machines to the LIS members.

Two boards for ABP staff positions have taken place: one for collective effects (ICE section) offered to T. Pieloni and the second for CLIC/CTF3.

IEFC last week: among other presentation from Elias on MD strategies and preliminary results. Gianluigi reminded at the meeting that we have still issues with the instrumentation preventing or slowing down progress with studies and MTE commissioning: among others BCTs for injection and extraction efficiencies in and from PS, BPM in the SPS

LHC: achieved more than 1 pb^-1 in integrated luminosity at 3.5 TeV so far with more than 700 nb^-1 in the last week. Peak luminosities up to 4x10³⁰ cm^-2s^-1 have been achieved. Efficiency for physics was close to 40 % with minimum turn-around time of 4 hours and 10 mins. During some of the fills sudden loss signals on few BLMs have been seen. The reason for that is not yet known.

The strategy for achieving 10³² cm^-2s^-1 by the end of the LHC proton run has been discussed at the last LMC. There was unanimity that we should continue with a beta* of 3.5 m and inject up to 432 bunches. It is not yet clear whether we will use bunch trains with 150 ns bunch spacing or whether we will go immediately to 75 ns spacing.

Gianluigi will be on holidays from Friday 13/8 to Sunday 29/8 included.

Injection loss studies (Sandra and Lucas) - slides Sandra - slides Lucas

Sandra presented the latest results of the studies she is conducting to understand the losses st injection in the PS affecting the radiation levels on Goward road. Measurements of the beam losses in the injection area and their evolution over time after injection have been performed with ACEM and LHC BLMs. LHC BLMs are ionization chambers and ACEM are photomultipliers. The time resolution of the LHC BLMs is poorer as compared to the ACEM as well as their sensitivity. ACEM sees losses right at injection and then at the second turn. Some oscillations are observed on the LHC BLM right after the injection which is a fake probably due to ion collection. As a result of that we can conclude that LHC BLMs cannot be considered as a replacement for the ACEM. BI is now looking into options for possible other solutions. Bettina mentioned that the same problem exists for LINAC4 and PSB where it is proposed to replace the BLMs with LHC BLMs.

Christian mentioned that fine time resolution might not be required for the PSB given that the injection process is taking place over several turns. The size of the ionization chambers is probably too large for the PSB. Large BLM (as those installed in the LHC) might lead to lose the possibility of distinguishing losses in different PSB rings. Furthermore it might be difficult to find the space to install the chambers.

The losses at injection measured with a TOF beam are approximately constant in the BLMs 42-43 and 45. BLM 44 is showing a higher signal (almost double). It could be due to the fact that this section is empty. The gain for this BLM is being checked.

Losses increase linearly with intensity. The horizontal emittance is kept constant as a function of intensity while the vertical emittance is increasing. It seems therefore that injection losses are mostly occurring horizontally. The dependence of the injection losses as a function of the injection trajectory has been studied and the present settings seem to be optimal.

Turn-by-turn measurements on the CNGs show losses which are maximum at BLM43. Tunes are 6.11 and 6.22. For the TOF beam losses are maximum at BLM42.

The tune is different for CNGS and TOF cycles. The FFT of the time signal of the spectra is being performed to understand the time pattern and the possible origin of the losses.

Michel asked what is the sampling interval of the scope in order to be sure that there is no aliasing effect. Simone replied that the sampling frequency is 1 Gs/s well above the typical spectrum of the signals observed

Gianluigi asked whether attempts to reduce the horizontal size of the beam have been performed by changing the optics of the injection line. Sandra replied in the negative adding that the injection line is not totally PPM. Gianluigi suggested to request some dedicated (vs. fixed target physics) time for that.

Lucas presented the status of the simulation of the orbit and aperture of the injection area with MADX. Estimation of the losses have been performed by assuming gaussian beams. Gianluigi suggested to measure what is the population of the tails in order to better estimate the amount of losses. This can be done by cutting the tails by scraping just before extraction form the PSB.

Lucas is also trying to simulate the observed loss patter in the ACEM with FLUKA taking init account the magnetic field effect.

Round Table

• Wire scanners in the PS are not working as well as for the SEM wires. Ana is back today. Only the OTR are working. MD4 is recovered
• The effect of the harmonic of the frequency of excitation of the damper on the capture has been studied on MD4. It seems that the capture efficiency is less dependent on the harmonic chosen for this cycle as compared to others where longitudinal coupled bunch instabilities are not dumped.
• Experiments are ongoing to use the CT extraction elements and in particular the electrostatic septum for the MTE extraction. One of the major issues is to see whether enough strength is available in the electrostatic septum to jump the magnetic septum blade without QKE.

Penelope:

• She is running numerical simulation of the heat conduction for the PSB simulation. She is presently using a simple mono-dimensional approximation to understand the problem. Christian noted that the model should be made more realistic and analytical and semi-analytical approaches should be pursued as well.

Christian

• LEIR: new settings have been implemented for the the e-cooler to reduce the cooling time. It worked well.
• The lead source was working well initially but the performance has degraded after the refill of the oven with lead. Michel added that several controls problems are being fixed

Gersende:

• She is working on a proposal to conduct tests to qualify the performance of RF cavities in terms of maximum achievable gradient in a solenoidal magnetic field for the neutrino factory front-end. She is getting support from RF people to get an estimate for manpower and money to test. The proposal for a test at CERN is supported by MICE if feasible by the end of 2011 because for the moment they cannot perform the experiment and they are waiting for the delivery of a coupling coil. Gersende is also working on the 44 to 88 cavity scheme.

Hannes:

• Hannes and Yannis are finalizing the layout and lattice of the PS2 injection. Hannes has transmitted information on lattice and magnetic errors for PS2 to the LARP colleagues so that they can run simulations for space charge.
• The PS2 collimation is being finalized with Javier. Dynamic aperture and non-linear dynamics simulations are being finalized.
• The study of the SPS lattice with low gamma transition for the moment on hold.

Next meeting

Monday, 6^th September 2010 at 14:00 in room 354-1-001

Agenda

• General information (Gianluigi)
• Round table (all)

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