2 Nov 2017 AMereghetti 2 R Bruce D Kodjaandreev A Mereghetti S Redaelli BSalvant G Valentino L ZammitMangion MD Merit The contribution from collimators to ID: 796360
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Slide1
Slide2MD2901: Asymmetric Collimator Settings in IR7
2 Nov 2017
A.Mereghetti
2
R. Bruce, D. Kodjaandreev, A. Mereghetti, S. Redaelli, B.Salvant, G. Valentino, L. Zammit-Mangion
Slide3MD Merit
The contribution from
collimators to
the LHC impedance budget is dominated by
IR7 carbon collimators:TCPs (3 per beam): their mm-gaps are among the smallest ones;TCSGs (11 per beam): their mm-gaps are quite small, and they are many;
2 Nov 2017
A.Mereghetti
3
Asymmetric settings:
One jaw is set at the required (working) position;
The other jaw is fully or partially retracted;
N.
Mounet
et al.
, IPAC13, pagg. 1817 – 1819;
Real part
Imaginary part
Example: contribution to total vertical dipolar impedance, 4TeV, squeezed optics, 2012 collimator settings
Effects:Reduce impact to impedance;Potential degradation of the performance (cleaning inefficiency);
The
merit of the MD is to
verify with beam
the feasibility of such asymmetric settings of the IR7 TCPs or
TCSGs in terms of
cleaning inefficiency
and
impedance
(tune-shift
measuremetns
);
Measurements can be
beneficial
for future
LHC
o
peration
and for
HL-LHC
!
Slide4Main activities
:
Perform LMs with one jaw of selected TCPs and/or TCSGs retracted, one at a time;
list of collimators and LMs still to be finalized;
Verify impact on impedance for the most promising configurations (i.e. minimum worsening of cleaning inefficiency) via tune-shift measurements;2 Nov 2017A.Mereghetti
4
Requests
:
8h
MD time;
Measurements at
FT
(no
Q-change/squeeze/collisions – i.e. b
*=1m);
1 or 2 nominal bunch + as many pilots
as possible (respecting SBF);
Tests on both beams – emittance not relevant;Use of ADT for LMs (standard tool) and for impedance measurements (AC-dipole kick mode);
Procedure
Nota Bene
:
The MD activity may require
2 ramps
, depending on number of configurations;
When exploring
asymmetric settings of TCPs
, measurements can be re-used for improving knowledge of
BLM response
- better insight into load on collimation system;
Short follow-up from MD2191
(IR7 Hierarchy limit): before dumping, we would like to perform a B1V LM with 1
s
TCPs-TCSGs retraction and TCSG.D4L7.B1 with the tilt angle, to assess:
reproducibility of curing the hierarchy breakage;
stability of angular alignment