Minutes of the LII Section meeting held on 6^th March 2006.

Present: G. Arduini, C. Carli, G. Bellodi, H. Braun, R. Bruce, M. Chanel, S. Gilardoni, J. Jowett, M. Martini, S. Maury, J. Pasternak, F. Roncarolo.

General information (G. Arduini)  (slides)

Collimation for heavy ions: status of studies (G. Bellodi) (slides).

As a result of the study all the future simulations should be performed assuming an average impact parameter of about 700-800 microns and the correct material density for the collimator jaw material (Carbon-Carbon 1.7 g/cm³). For the moment the study has been performed only for beam 1 because of a problem in the generation of the beam 2 aperture and optics data. This has been now fixed. Furthermore the data concerning the aperture contained still a few small errors.

The files corresponding to the optics that will be used during LHC commissioning with ions and for the early and nominal ion runs (including beta* and separation bumps) in collision and pre-collision should be made available and the corresponding files for ICOSIM should be generated for beam 1 and beam 2 with the corrected aperture data from S. Redaelli. It was agreed that the data for the optics and the aperture should be provided in a single TFS file (already available). Action: J. Jowett.

There was some discussion about the implementation of effect of the orbit distortion. This should be implemented in ICOSIM as early as possible to study the effect of closed orbit distortion and separation bumps on the loss pattern. Action: H. Braun

It was agreed that a possible set of realistic orbits should be produced with MAD-X. A similar approach to that used for the proton collimation studies should be followed. Action: J. Jowett to follow-up with the proton collimation colleagues.

The presently known loss pattern (including BFPP in IR1, IR2, IR5) should be compared with the localization of the Beam Loss monitors to identify the additional requirements in terms of monitors. Action: S. Gilardoni will circulate the present list of locations of the BLMs and he will organize a discussion with H. Braun, G. Bellodi and J. Jowett to prepare a proposal to be discussed with B. Dehning.

Simulation of BFPP measurements at RHIC (R. Bruce) (slides)

A very good agreement has been found between the measured and simulated beam loss pattern in RHIC. This gives some hope that the beam loss pattern in the LHC can be determined within a couple of metres. The beam loss pattern has been determined for IR2 and it is being evaluated for IR1 and IR5. The effect of orbit errors has not been studied yet and should be performed using a similar approach to proton collimation. Action: J. Jowett, R. Bruce.

The measured BLM signal at RHIC is still smaller than the expected one (by a factor 2?). H. Braun suggested that this could be due to pile-up of the signal of Minimum Ionization Particles in the PIN diodes. It is therefore important to estimate the number of MIPs per lost ion. Action: R. Bruce.

Round table

C. Carli, M. Chanel, J. Pasternak, F. Roncarolo: working on LEIR. Optics installed for the injection line based on measurements of the Twiss and dispersion parameters at the exit of LINAC3. There are some doubts about the value of the dispersion and Twiss parameters at the electrostatic septum. The beam focus seems to be upstream of the electrostatic septum. This could explain the low injection efficiency obtained so far (~25 % instead of 50 %). Measurements of the Twiss parameters in the ETL line and dispersion measurements in the last two screens before the electrostatic septum should be performed in order to clarify the situation as there are some doubts on the measurements performed at the exit of the LINAC3. Action: C. Carli, F. Roncarolo.

Cooling in the transverse and longitudinal plane has been observed although the ion and electron beam do not seem to be aligned. There are some doubts about the electron beam position as measured by the pick-ups.

During the week efforts will concentrate to understand the injection line optics and efficiency and the electron cooling. In case higher injection efficiencies can be obtained then optics measurements should be performed and the collimation system should be commissioned.

M. Martini is finalizing a note on the optics for the TT2 line based on the last measured initial parameters for the line and including the latest HW modifications. He is also following the alignment of the TT2 line. This year only a preliminary alignment will be possible due to the important displacements observed and due to the presence of magnets preventing a precise measurement of the present geometry of the line. These magnets cannot be removed temporarily now due to lack of time.

J. Jowett has provided an updated parameter list for LHC (including ions) for the Review of Particle Properties.

S. Gilardoni presented the status of the dipole allocation work. Nearly 5 sectors have now been assigned (18 magnets last week). The results of the analysis on some wires used for the PSB and PS have been transmitted from S. Sgobba's team. The data indicate that the wires did not broke as a result of the interaction with the beam but probably as a result of other mechanical stresses. He could not complete the estimation of the beam profile evolution of the CNGS beam in TT2-TT10 as part of the study of the beam loss and radiation estimations in the PS-SPS complex. S. Gilardoni will complete it by tomorrow. Action: S. Gilardoni.

Next meeting and tentative agenda

Monday, 20^th March 2006 at 09:00 in room 354-1-001

General information (G. Arduini)

TT2-TT10 transfer for the CNGS beam. Study of the potential loss points. (S. Gilardoni)

Optics parameters for the LHC ion commissioning and early and nominal runs (beta*, crossing angles, etc.) (J. Jowett)

Preliminary results of the simulation of the H- injection of LINAC4 into the PS Booster (M. Martini)