Minutes of the LIS Section meeting held on 27 August 2012

Present: Androula Alekou, Gianluigi Arduini, Hannes Bartosik, Michael Bodendorfer, Christian Carli, Vincenzo Forte, Adriano Garonna, Simone Gilardoni, Antoine Lachaize, Meghan McAteer, Yannis Papaphilippou, Tatiana Rijoff, Guido Sterbini, Adrian Ulsroed, Raymond Wasef.

General Information (Gianluigi)

Gianluigi welcomed Androula (Marie-Curie Fellow in the frame of the LAGUNA project under the supervision of Yannis), Meghan (Marie Curie oPAC fellow working on the PSBooster optics modellization under the supervision of Christian and Rogelio Tomas) and Tatiana (PhD student working at the estimation of the colective effects for the ELENA ring under the supervision of Christian and Alexey Burov).

Gianluigi reminded the team of the new rules in force concerning the compulsory protection equipment necessary for accessing the PS-SPS Complex (DSO memorandum circulated after the meeting) and of the new compulsory web training for the PS comoplex. Passing this test will be a necessary condition to obtain or maintain access rights in the PS Complex (e-mail sent after the meeting).

Gianluigi reminded the team that a student from Hamburg, O. Stein, will be visiting CERN on 12/9-13/9. He would like to start a PhD study here at CERN. Anybody interested to meet him should contact R. Schmidt

Haixin Huang (BNL Booster group leader) will visit CERN from 15/10 to 26/10.

LHC status:

12.8 fb^-1 have been delivered so far and peak luminosities in excess of 7.7x10³³ cm^-2s^-1 have been achieved thanks to the excellent quality of the beams delivered by the injectors which has reached unprecedented values. Bunch intensities close to 1.6x01¹¹ p have been injected in the LHC. Gianluigi asked what were the main changes applied to the machine settings to improve the LHC beam brightness. Simone replied that the brightness of the beam has been increased in the PSBooster by tweaking the optics of the LINAC2 to PSB transfer line, the low energy working point has been otpimized as well as the working point at extraction when the beam was getting unstable from time to time. Simone mentioned that at this bunch intensities the PS is operating close to the instability limit at low energy and therefore no significant bunch intensity increase should be expected.

Highlights from NuFact2012 (Simone) - slides

Christian asked whether it is understood why the number of nu tau events at CNGS was larger (4 to 5) then the number detected (2 to 3) and what is the expected background. Simone replied that the detector efficiency mudt be taken into account and that the data have not yet been completely analyzed. The expected background is much less than 1.

Round Table (all)

MTE (Antoine, Simone):

Another issue has been discoverd in the orbit acquisition and it is not clear yet whether there is a front-end software or hardware problem. It seems that in some cases the parameters for the acquisition are not loaded correctly and the sum signal is saturating falsing the measurement. Gianluigi asked whether the sum and delta signal can be logged so that the "bad" measurements can be discarded. Simone replied that at present it is not possible to log both sum and delta signal. Simone noted rightly that it is important to understand and solve the issues with the PS orbit system taking into account that the same system is going to be deployed also in teh PS Booster.

The MTE capture has been resumed but at present it is not possible to run in parallel to CNGS because of the limits on the total acceptable losses.

Simone noted that the issues observed with the orbit system prevents or at least hampers significantly the setting up of the hybrid extraction scheme.

TT2-TT10 matching for the LHC beam (Adrian, Hannes, Yannis, Simone).

The OTR screens in TT2 are now working. Measurements in TT2 have been taken. Gianluigi suggested to take data at the same time in TT2,TT10 and in the SPS and to measure also the betatron mismatch so to rematch the full parameter set.

Q20 optics (Hannes, Yannis)

The 50 ns beam has been delivered to the LHC with the Q20 optics with quality equivalent or better than that obtained wih the Q26 optics. The longitudinal emittance of the delivered beam was smaller than that delivered with the Q26 optics and a transfer with an intermediate value has benn tested showing no significant increase in the cpature losses in the LHC. It must be noted that a batch-by-batch longitudinal blow-up is being implemented in teh LHC and could alleviate any issue related to IBS arisign from teh smaller longitudinal emittance. In summary the test was very succesful.

Gianluigi suggested to compare the tail population for a high intensity 50 ns beam delivered with the Q20 optics and with the Q26 optics as this could be another stron motivation for moving fast to the Q20 optics. The 25 ns beam must be tested as well with the Q20 optics as it was not done recently.

Space charge studies in the PS (Raymond)

A distribution of the magnetic errors for the PS has been provided by the magnets group and should be introduced in PTC-ORBIT.

The simulations are still quite long and it takes about 10 days to simulate 25 ms of beam time. Beam measurements indicate that a skew sextupole resonance is dominant. An application to measure resoance driving terms should be ready soon. Tests are continuing to reduce the space charge tune spread at injection by increasing the dispersion and therefore the beam size exciting the gamma jump triplets.

Space charge studies in the PSB (Vincenzo)

Quadrupolar field errors have been introduced in teh simulations and 5 ms of beam can be simulated in ~12 hours. Gianluigi asked whether the quadrupolr errors have been introduced based on the correction that are applied to compensate beta beating. Vincenzo replied in the negative. Gianluigi replied that ot would be important to use the estimated values as these should provide a relaistic basis.

Vincenzo is also working at providing a more relistic distribution for the high intemsity beams.

PS damper (Guido)

The PS damper has been tested in both planes and the reduction of the damping time of the injection oscillations has been measured. At the moment only one plane at a time can be operated as only one electronic card is available but a second one is ready to be installed. There are indications that the head tail instability observed on the TOF beam at injection can be dumped as well.

Gianluigi encouraged to put in operation the transverse damper and in particular for the LHC beams where it could have the beneficial effect of reducing the sensitivity to injection errors and the drift in the trajectories of the beams delivered by the PSBooster.

From Cedric (e-mail as he could not be present)

I have the candidacy exam for the EPFL on Wednesday. I had to write the research plan and prepare the presentation. Lenny agreed on the content so I now have to give a very good presentation and that should be alright. Concerning the MTE work I worked on the theoretical aspects while the summer student (C. Frye) was with us. We also collaborated with A. Bazzani which was at CERN for one week. We made good progress and the agreement between the theory predicting the fraction of particles trapped in the islands and the numerical simulations (with the code I wrote when I was technical student and which has been adapted for the new models we consider) is promising. We are preparing an internal note. On the other hand we made progress for the dummy septum: we started tracking simulations including the interaction with the blade (Monte Carlo with Fluka - with S. Damjanovic - combined with PTC tracking in the magnets and the rest of the machine). This uses a realistic beam distribution representing the "integrated" effect of the time dependence of the fast extraction bump, with the beam passing from one side of the blade to the other. From these simulations we already obtained preliminary results on the efficiency of the scheme (reduction of the losses at the magnetic septum 16 as a function of the positioning of the blade and also total losses induced in straight section 15 due to the interaction with the blade). I don't quote any number yet, I hope to present first results at the dummy septum meeting on Thursday.

Next meeting

Monday, 17^th September 2012 at 14:00 in room to be defined

Agenda:

To be defined

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