Minutes 23rd LEB Meeting – blg 112-R-028 – 10h00, 8 October 2012_version 1
People in attendance:
Kaan Vatansever
Mark Antony Gallilee
Benoit Salvant
Gloria Corti
Helmut Burkhard
Massimo Giovannozzi
Massimiliano Ferro-Luzzi
Bernhard Holzer
Jorg Wenninger
Christoph Schaefer
Austin Ball
Rolf Lindner
Kaan.Vatansever@cern.ch
mark.antony.gallilee@cern.ch
Benoit.Salvant@cern.ch
Gloria.Corti@cern.ch
Helmut.Burkhardt@cern.ch
Massimo.Giovannozzi@cern.ch
Massimiliano.FerroLuzzi@cern.ch
Bernhard.Holzer@cern.ch
Jorg.Wenninger@cern.ch
Christoph.Schaefer@cern.ch
Austin.Ball@cern.ch
Rolf.Lindner@cern.ch
TE-VSC-EIV
TE-VSC-EIV
BE-ABP-ICE
PH-LBD
BE-ABP-LCU
BE-ABP-LCU
PH-LBD
BE-APB-LCU
BE-OP-LHC
PH-CMX
PH-CMX
PH-LBO-DO
Description and summary of the Meeting:
The meeting was held in order to go on with the study of the LHCb VELO Upgrade that was discussed
in the last LEB Meetings. The main purpose was to introduce beam parameters after LS2 and for HLLHC, which then gives a basis for the final aperture verification for the VELO RF Foil.
Bernhard Holzer has given an overview about the nominal parameters on the basis of the HL-LHC
parameters. The HL-LHC Parameter & Layout Committee can be found under:
https://espace.cern.ch/HiLumi/PLC/default.aspx
The direct link to the nominal HL-LHC parameters:
https://espace.cern.ch/HiLumi/PLC/_layouts/xlviewer.aspx?id=/HiLumi/PLC/SiteAssets/Parameter%
20Table.xlsx&Source=https%3A%2F%2Fespace%2Ecern%2Ech%2FHiLumi%2FPLC%2FSiteAssets%2FF
orms%2FAllItems%2Easpx&DefaultItemOpen=1
The following information was given during the meeting. Full presentations can be found on the LEB
Indico page at https://indico.cern.ch/conferenceDisplay.py?confId=209136
Kaan Vatansever, TE-VSC
Update on parameters (b*/crossing angle α)- presented by Bernhard Holzer
The parameters shown in the presentation are the official parameters set in the HL-LHC Parameter &
Layout Committee.
The foreseen Luminosities are within the range of L=2*1033 up to L=1*1034 . Following table shows an
overview of the used parameters:
LHC Standard
HL-LHC 25ns
HL-LHC 50ns
Np
1.15*1011
2.2*1011
3.5*1011
nb
2808
2808
1404
β*
3m
3 -10 m
3-10 m
εn
3.75 μm
2.5 μm
3.0 μm
σ
18 μm
7.6 μm
8.3 μm
Table 1 Parameters used for Luminosity calculations
Luminosities are within the range of the expected, but require levelling due to the requirements of
the LHCb detector. The goal for the total beam separation was set to 10σ (+/-5σ) to avoid parasitic
crossings. A vertical crossing angle α of 100 µrad is enough to ensure a separation for a β* range
from 3-10m.
Concerning a horizontal crossing angle slides were shown which indicate that a run at 25ns would
lead into a non sufficient separation. This is the case for a positive kick on beam 1, due to the LHCb
spectrometer.
It was proposed to rotate the beam screens by 90 degrees to solve this, but the radiation level needs
to be verified in order to make sure a modification is possible. LS1 would be the best time to make
this modification.
As a general request Helmut Burkhard asked for a wider examination of possible beam parameters
to give the most running flexibility. As a guideline a factor 5 was given for β* levelling (this value is
the official HL-LHC ration between leveled and virtual luminosity), which increases the β* range from
3m to 15m, instead of the analyzed 3m to 10m.
LHCb VELO aperture verification with MADX- presented by Massimo Giovannozzi
For the aperture verifications a vertical crossing angle was taken as an assumption. This should be
the case after LS2 and for the HL-LHC. In addition vertical crossing angle was the operational mode
for 2012 at top energy, whereas for injection a horizontal angle was used.
The following case was assumed for the new VELO aperture calculations. Smallest radius equivalent
to 3.4 mm for ± 800 mm around IP. Tolerances of 100 μm closed orbit stability (50-60 µm seen
during runs), 100 μm mechanical, and 100 µm separation, added linearly.
Kaan Vatansever, TE-VSC
•
Assuming the above tolerances and that a vertical crossing angle will be used to separate the
beams, then:
–
The new VELO aperture (beginning of fill): 63 σ (assuming 25 ns nominal emittance
at β* 3m).
–
The new VELO aperture (beginning of fill): ≈31 σ (assuming 25 ns nominal emittance
at β* 10m).
The general running goal for LHCb for HL-LHC must be to find a suitable solution for a vertical
crossing angle from injection up to top energies, otherwise parasitic crossings will occur. The real
apertures will be measured during MD Block 3 on Saturday, the 13th of October from 00h00 to
02h00. After this the situation should be clearer, results will be discussed in the next LEB Meeting.
Overview of Actions
Action
Organize LMC approval for upper limit on minimum
radius of upgrade VELO RF foil in STABLE BEAMS (post
LS2) – check availability with Brennan/Frank
Check impact of upgrade VELO RF foil inner radius on
impedance and power dissipation (R_foil from 5.5 mm,
as now, to below 3.5 mm; for more info, ask Massi).
Check dependence of dynamic vacuum effects on
upgrade VELO RF foil inner radius, gap between the
two sides remains unchanged (for more info, ask
Massi)
Re-check machine protection settings to prevent beam
from being driven into the VELO
Report on MD run with respect to measured aperture
Suggest alternate for LEB meetings
Additional Information:
Next Meeting: 26 October 2012 at 10h00 in 112-R-028
Kaan Vatansever, TE-VSC
Responsible
M Gallilee
Date Required
Mid-Nov 2012
B Salvant
26 Oct 2012
G Lanza
26 Oct 2012
J Wenninger
26 Oct 2012
B Holzer
All Members
26 Oct 2012
26 Oct 2012