Results from crystal–assisted
collimation test in LHC
09/11/2015 – LHC
29/11/2016
UA9 Study
Collaboration
Workingboard
Group
Roberto Rossi, Daniele Mirarchi, Stefano Redaelli
Roberto
RossiS. Montesano, F. Galluccio, A. Masi,
W. Scandale,
Daniele
Mirarchi,
Stefano C.
Redaelli,
Scandale
G.
Valentino,
M. Butcher,
Barreto,Walter
A. Rijllart,
P. Serrano Galvez
Outline
• Introduction
• Ramp function preparation
• Ramp function test
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Planned goals for 2016




Channeling and cleaning of ion beams at top energy
Collimation cleaning for protons at 6.5TeV (loss maps)
Maintain channeling during energy ramp
Repeat some detailed measurements no satisfactorily performed in 2015/2016
(bending angles, V crystal at top energy, collimator scans, etc...)
Also the chance to have several tests gives an opportuinity to address the stability of
hardwere
MD assigned
1. July the 29 (devoted to complete detailed measurement and loss maps)
2. October the 30 (energy ramp)
3. Next Tuesday? (ion test at top energy)
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Ramp function
To generate the ramp function we started from the energy ramp function for the LHC.
Need to add the angular rotational stage to the standard position versus time applied to the primary
collimators.
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Ramp function – first test
A couple of test were performed during the last proton MD
The first generation of goniometers have not the required precision on the absolute
reference for both axis, hence two ramps were tested:
1. first test with functions generated from alignment positions of MD1, re-adjusted
from injection positions (high risk of problems) with both crystals
2. Second ramp with functions updated based on lasted alignment positions at
injection and top energy
How to observe the channeling during the ramp?
continuous loss maps during the ramp (as already tested for standard collimation
earlier this year), to look at the loss pattern
When in channeling losses at crystal are low, while increase at absorber position, after the
absorber the collimation hierarchy is visible
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Ramp function – Goniometer
Data are averaged over a second (raw data rate 10 Hz), also RMS is calculated
RMS shows the high stability of linear stage, and a stability within
the critical angle for rotational piezo-electric stage
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Ramp function - Loss Maps
Loss maps recorded during the energy ramp.
absorber
crystal
The horizontal
ramp case is
presented
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Conclusion
 Channeling quickly re-established with both crystals, at both energies
 Cleaning performances has been measured showing a general improvement of leakage in
IR7-DS
•
Simulations, to investigate the reduced efficiency of horizontal crystal are ongoing
 Ramp function has been successfully tested
•
Great achievement for the piezo-goniometer technology, further improvements of stages
stability are foreseen for the second generation goniometer (to be installed on b2 this winter)
Goals for crystal collimation:
 Finalize open issue in data analysis,
o in particular about linear scan measurement deeper discussion and investigation is needed
o Losses and goniometers oscillations frequency spectrum analysis
 Continue experimental activities before end of the year
Test with ion beam @ 6.5 Z TeV
 Complete simulations to benchmark code with experimental data at 6.5 TeV (linear scans,
angular scans, loss maps )
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backup
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Introduction
y [mm]
Crystal
TCSG
TCLA
IR7 betatron collimation layout
TCPs TCSGs TCLAs Crystals
40
30
In the pictures is possible to see how crystals are
integrated in the present collimation system.
20
10
6s
0
x [mm]
Crystal
-10
40
19800
19900
TCSG
20000
20100
TCLA
20200
s [m]
30
In 2015 for the first time channeling has been
observed with protons at LHC flat top and ions at
injection energy.
This was the first step to a crystal based
collimation layout.
20
10
6s
0
-10
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The beam trajectories are presented for 7 TeV
In red the beam envelope @ 6 σ
In gray the deflected particle trajectories (50 μrad)
19800
19900
20000
20100
20200
W. Scandale et al., “Observation of channeling for 6500 GeV/c protons in the crystal assisted collimation
setup for LHC”, Physics Letters B 758 (2016) 129-133
s [m]
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Injection checks – angular scan
Same measurements of 2015 to re-establish channeling and check the goniometers angular position.
Crystal @ 5.7 σ
Best CH @ 2067.5 μrad
Also vertical crystal has been tested,
alignment position and channeling
angle had been used to generate the
ramp function
Hor Crystal BLM / Beam Flux / AM losses [a.u.]
Horizontal Crystal Angular Scan @ 450 GeV 2016-07-29 13:09:00
1
10-1
1940
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1960
1980
2000
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2040
2060
2080
2100
2120
Horizontal Crystal Angle [ mrad]
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Injection checks – linear scan
Linear scans were also repeated at injection
Horizontal Crystal Scraping @ 450 GeV
´10
difference observed between kick angles
at injection and flat top.
Investigation is on going.
main suspects: beta beating, systematics
errors
[0]+[1]*TMath::Erf((x-[2])/[3])
0.1
´10-12
c2 / ndf
Hor Absorber BLM / Beam Flux [a.u.]
-12
3
c2 / ndf
p0
p1
p2
p3
1.546e-25 / 29
9.579e-13 ± 2.143e-14
9.576e-13 ± 2.951e-14
-63.57 ± 0.4423
11.71 ± 1.034
2.5
2
1.5
1
3.377e-30 / 97
Constant 9.269e-14 ± 5.438e-16
Mean
-63.58 ± 0.007346
Sigma
8.254 ± 1.34e-14
0.08
0.06
0.5
0
-100
-80
0.04
-60
-40
-20
0
Deflection angle @ absorber position [ mrad]
0.02
0
-100
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-90
-80
-70
-60
-50
-40
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Flat top – linear scan
Also in 2015 data we observed a difference between the angle measured at injection and the one at flat top
The difference is around 10 urad
Investigation is on going, the main
subjects are about the machine optics
(beam size), and possible systematics
errors in this kind of procedure.
Horizontal Crystal Scraping @ 6500 GeV
Hor Absorber BLM / Beam Flux [a.u.]
Here the comparison is presented for
Horizontal crystal
´10-12
10
c2 / ndf
p0
p1
p2
p3
5.945e-25 / 22
1.209e-12 ± 6.7e-14
1.008e-12 ± 8.513e-14
-74.24 ± 0.5644
5.423 ± 1.13
8
6
4
[0]+[1]*TMath::Erf((x-[2])/[3])
´10-12
c2 / ndf
0.22
1.744e-29 / 97
Constant 2.106e-13 ± 1.12e-15
0.2
Mean
0.18
Sigma
2
-74.23 ± 2.146e+04
3.824 ± 9.517e-15
0.16
0.14
-100
0.12
-80
0.1
-60
-40
-20
0
Deflection angle @ absorber position [ mrad]
0.08
Also comparison with simulations will be performed to investigate this issue
0.06
0.04
0.02
0
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-90
-85
-80
-75
-70
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Flat top – angular scans
Vertical crystal was tested for the first time this year, also horizontal crystal was tested
Horizontal Crystal @ 5.5 σ
Vertical
@ 5.5
σ Top
Vertical
CrystalCrystal
Angular Scan
at Flat
Vertical Crystal BLM / Beam Flux [a.u.]
Hor Crystal BLM / Beam Flux / AM losses [a.u.]
Horizontal Crystal Angular Scan @ 6500 GeV 2016-07-29 15:49:00
AM
1
10-1
AM
1
10-1
CH
CH
1960
1980
2000
2020
2040
Horizontal Crystal Angle [ mrad]
2160
2170
2180
2190
2200
2210
2220
2230
Vertical Crystal Angle [ mrad]
Both crystal shows a pretty similar behaviour, and also Reduction Factor (RF) are pretty close
Hor RF = 26.9
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Ver RF = 23.5
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Loss Maps – Vertical Best case
Set up for crystal collimation:
TCPs and TCSGs upstream out
Everything else at nominal aperture
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Loss Maps – Vertical Best Case
Set up for crystal collimation:
TCPs and TCSGs upstream out
Everything else at nominal aperture
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An improvement of a factor 9 is
observed in IR7DS, a factor 14 is
observed in IR3
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Ramp function
Ratio of losses between crystal and absorber position
Systematic analysis about
the performances during
energy ramp is on going
◼ 1st ramp -hor
● 1st ramp - ver
▴ 2nd ramp - hor
This is a first attempt about
those kind of studies
Excellent results
Channeling achieved at
flat top close to the
alignment measured in
July
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