Transcript SPS & PS Experiments Committee October 22nd, 2013 CERN, Geneva, Switzerland Status of the UA9 activities Stefano Redaelli, BE-ABP on behalf of the UA9 collaboration Special.

SPS & PS Experiments Committee
October 22nd, 2013
CERN, Geneva, Switzerland
Status of the UA9 activities
Stefano Redaelli, BE-ABP
on behalf of the UA9 collaboration
Special acknowledgements: D. Mirarchi, S. Montesano, W. Scandale.
Outline
Introduction
SPS-UA9 layouts
Recap. of main results
Activities in the last year
Prospect for LHC tests
Conclusions
S. Redaelli, SPSC, 22-10-2013
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Introduction
Bent crystals allow bending high-energy particles
trapped between lattice planes, with reduced nuclear
interactions compared to amorphous scatterers.
UA9 MISSION: investigate bent
crystals as primary collimators
in hadron colliders.
Amorphous (0.6 m CFC)
<θ>MCS ~ 3.4 μrad (7 TeV)
Crystal
(Channeling)
(3 mm Si)
<θ> ~ 40-50 μrad (7 TeV)
Standard collimation
•
In the crystal, particles are subjected to a
coherent interaction (channeling):

large angle possible for high-energy particles;

reduced probability of diffractive events and ion
fragmentation/dissociation.
• BUT

Beam
Primary
Secondaries
Absorbers
Crystal-based collimation (ideally)
small angular acceptance (2×θc);
Uncertainties on the extrapolation to unknown energy territories
 localization of the losses on a single absorber.
and operational challenges call for solid experimental validation
Crystal
before this technology can be relied upon for future designs.
Beam
???
S. Redaelli, SPSC, 22-10-2013
Absorber
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UA9 experimental achievements
•Prototype crystal collimation system in CERN-SPS (~ 5 days per year):
• 2009 ➙ First results on the SPS beam collimation with bent crystals.
(Physics Letters B, vol. 692, no. 2, pp. 78–82).
• 2010 ➙ Comparative results on collimation of the SPS beam of protons and Pb ions with bent crystals.
(Physics Letters B, vol. 703, no. 5, pp. 547–551).
• 2011 ➙ Strong reduction of the off-momentum halo in crystal assisted collimation of the SPS beam.
(Physics Letters B, 714(2-5), 231–236)
• 2012 ➙ Halo population reduction in dispersive areas, SPS loss maps, optimized apertures for
collimation system elements, …
(Physics Letters B, 726 (2013), 182–186)
•Test beams at CERN North Area (~ 3 weeks per year):
• Study of crystal – beam interactions: characterization of single-pass cross sections.
• Characterization of experimental apparatus (goniometers, detectors, ...) prior to SPS installation.
• Measurement of crystal properties before installation in CERN-SPS.
•New HiRadMat facility starting 2012 (1 experiment for UA9)
• 2012 ➙ Robustness of crystal against high-energy, high-intensity beam impacts.
Scientific achievements presented to this committee
in detail in previous annual reports.
S. Redaelli, SPSC, 22-10-2013
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Outline
Introduction
SPS-UA9 layouts
Recap. of main results
Activities in the last year
Prospect for LHC tests
Conclusions
S. Redaelli, SPSC, 22-10-2013
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SPS layout
Throughout the years, the SPS UA9 setup has evolved thanks to new devices and profited existing
installations to achieve a very complete and reliable apparatus that enables:

Precise and reliable crystal alignment to the beam (using a two-side LHC collimator prototype).

Characterization of local losses through scans of crystal positions/angles and of absorber and detector scans.

Precise characterization of channeled beam properties (2D profiles with Medipix images)

Analysis of off-momentum losses at dispersive locations through local scraping and diagnostic,
representative of the LHC limiting loss locations.
S. Redaelli, SPSC, 22-10-2013
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Main SPS achievements
• Alignment (linear and angular) of the crystal is fast and well reproducible.
• Multi-turn channeling efficiency: 70÷80% for protons, 50÷70% for ions.
• Channeled beam observed with the Medipix.
• Loss rate reduction at crystal: 5÷20x for protons, 3÷7x for ions.
• Off-momentum loss reduction: 2÷6x for protons, 3÷7x for ions.
Protons
data
➙ This is what matters for the LHC, limited by dispersion losses!
• Loss maps: consistent reduction of the losses around the full ring when
simulation
comparing crystal in channeling and crystal in amorphous.
• Dependence of the off-momentum leakage on the clearance
between crystal and absorber (recent RPL).
• Test multi-strip crystals in
Protons
volume-reflection (new
from SPSC2012).
data
S. Redaelli, SPSC, 22-10-2013
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Channeling Pb ion beams
Pb ions
Pb ions
data
simulation
S. Redaelli, SPSC, 22-10-2013
data
simulation
A. Taratin at al.
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Recent analysis and simulations
Continued work on analysis and reproducing SPS results (multi-turn simulations).
Two recent examples:
- Characterization of channeled beam, crucial for design of LHC absorbers
D. Mirarchi et al., IPAC2013
- Detailed study of optimized SPS absorber settings for optimum cleaning in
dispersive
areas. A. Taratin et al., Physics Letters B, 726 (2013), 182–186.
Simulated distribution at
the Medipix from multi-turn
Measured Medipix data
D. Mirarchi at al., IPAC2013.
S. Redaelli, SPSC, 22-10-2013
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Multi-strip crystal tests
• Based on high efficiency volume reflection. Several crystals
carefully aligned used to increase the deflection angle.
• Potential benefit: large angular acceptance and efficiency.
• Drawbacks: larger nuclear interactions compared to
θref
channeling (still less than amorphous, but...). Crystals more
difficult to make.
θref
• A multi-strip crystal (MS16) previously characterized
in the North Area was installed in SPS during 2012:
• Not designed for SPS but for Tevatron (1 TeV)
• Single-crystal deflection at 400 GeV:θ = 28 μrad
• At 270 GeV, proved large acceptance of ~2000 μrad!
• More complex dynamics that standard crystals in
θref
θacc
VR
channeling ➙ need further studies with crystals
optimized for SPS to achieve conclusive results.
• Test of beam scraping in pulsed mode
Preliminary
analysis
~x1/3
(LHC type beam) with an orbit bump.
~2 mrad
Main paramaters:
- N. of strips: 16
- Single strip values:
- 1 mm x 72 mm
- Thickness: 0.3 mm
- Curvature radius: 1.4 m
S. Montesano et al.
S. Redaelli, SPSC, 22-10-2013
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Fixed-target experiments at SPS-NA
•Semi-permanent installation on the H8 beam line:
• optical fibers & cables, electronics (HNA443), tables and crystal alignment system
• tracking detectors, goniometer, GEM, Medipix (removed after each test beam)
•Crystal tested with primary beam at 400 GeV
• experimental optimization and characterization before deployment in SPS or LHC
• test-bench for crystal simulation tools
• “exotic” crystals (multi-crystals, crystals with variable curvature, ...)
• new physics (radiation production, interaction rates, ultra-thin crystals, mirror effect...)
S. Redaelli, SPSC, 22-10-2013
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Crystal mirror effect
• Properly designed flat crystals can steer particle beams through the
Thin
crystal
mirror effect (E. Tsyganov and A. Taratin, NIMA 363, (1995) 511-519).
• Observed in 2012 at SPS-NA with 400 GeV beams.
• Thin, flat (unbent) crystals with thickness λ/2 can reflect particles
impinging with an angle ~1/2 critical angle.
• 400 GeV: λ = 56 μm → crystal thickness = 28 μm.
• Using (110) plane of Si crystal.
• PL-B paper in preparation.
Incoming
beam
A. Mazzolari at el.
S. Redaelli, SPSC, 22-10-2013
Experimental result
Horizontal deflection angle [µrad]
deflection angle [µrad]
Horizontal
angle [µrad]
deflection
Horizontal
angle [µrad]
Horizontal deflection
Simulation
Horizontal incoming angle *[µrad]
Horizontal incoming angle *[µrad]
Preliminary analysis
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HiRadMat robustness test
• What is the dose that a crystal can withstand while
ensuring good channeling?
• IHEP U-70 (Biryukov et al, NIMB 234, 23-30):
➡70 GeV protons, 50 ms spills of 10 protons every 9.6 s,
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several minutes irradiation
channeling efficiency unchanged.
✓
• SPS North Area - NA48 (Biino et al, CERN-SL-96-30-EA):
➡400 GeV protons, 2.4 s spill of 5 x 10 p every 14.4 s,
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one year irradiation, 2.4 x 1020 protons/cm2 in total,
channeling efficiency reduced by 30%.
✓
• HRMT16-UA9CRY (HiRadMat facility, November 2012):
➡440 GeV protons, up to 288 bunches of 1.1 x 10 (25 ns)
✓no apparent damage to the crystal from accurate visual
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inspection
more tests planned to assess possible crystal lattice damage
A. Lechner et al., IPAC2013.
•
•
S. Redaelli, SPSC, 22-10-2013
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Plans for 2014
UA9 wishes to take data after the accelerator’s startup in 2014, in order to
continue advancing the crystal developments.
Requested beam time in 2014: 10 days in H8 and 2 days in SPS.
1. SPS ring
Test new detector with 45 deg. configuration. Now being tests in Rome!
Characterize crystals for the LHC in multi-turn regime.
Test/characterize new goniometer technologies for the LHC.
Understand better the potential of multi-crystal volume reflection.
Repeat measurements with HiRadMat crystal, to assess multi-turn behaviour.
2. SPS-NA line
Continue the measurements of new crystals for SPS and/or LHC.
Re-qualify the crystal that was stress-tested in HiRadMat.
Test new detector with 45 deg. configuration (if miss the SPS ring
installation).
3. Preparing for LHC MD’s
S. Redaelli, SPSC, 22-10-2013
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Outline
Introduction
SPS-UA9 layouts
Recap. of main results
Activities in the last year
Prospect for LHC tests
Conclusions
S. Redaelli, SPSC, 22-10-2013
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Why LHC tests?
Standard collimation
Bea
m
Primary
Secondaries
Absorbers
Promises of crystal collimation:
1. Improved DS cleaning in channeling;
2. Reduce impedance: less secondary
collimators and larger gaps;
3. Much improved cleaning for ion beams.
?
Crystal-based collimation
Bea
m
SPS-UA9: very encouraging results on key
“features” (reduced nuclear interactions, improved
Crystal
losses in dispersive areas, loss maps, ...).
???
Absorbe
r
But several open questions remain.
Scope of LHC test: MD’s with low beam intensities to address several questions:
- Can crystal collimation compete with the present very good cleaning system?
- Uncertainty for the scaling to higher energy (e.g.: single diffractive losses).
- Operational challenges much more complex than at the SPS (ramp, squeeze, etc...).
- Some outstanding machine protection concerns must be addressed.
Real need to improve the present system will be assessed in 2015 within the
context of the collimation upgrade plans.
S. Redaelli, SPSC, 22-10-2013
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Preparation for LHC beam tests
•Improved tools to identify suitable candidate layouts (semi-analytical analysis of channeled
beam trajectories). Minimum impact on layout: profit of existing collimators.
•Setup complete tracking simulations to predict loss maps
•Important to address cleaning performance taking into account layout constraints and
leakage from collimators used as absorbers.
•Worked on an improved crystal routine for tracking studies.
•Conceived set of setting for the whole collimation system (~100 collimators) to achieve MD
goals.
Example: layout for a H crystal
close to primary collimators. For
H and V planes, compared 2
layouts (4 cases) with crystals
close to primary or close to IR7
(lower radiations).
S. Redaelli, SPSC, 22-10-2013
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Simulated cleaning in LHC-IR7
Present system
According to simulations, the proposed
layouts should improve cleaning by a
factor ~5-10.
Crystal channeling
Crystal
amorphous
Final choice of channelling angle to be
stamped at the next collaboration
meeting in a few weeks (40 or 50 μrad)
D. Mirarchi at al.
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Development on crystal modelling
• Several crystal routine available:
Integration of equation of motion vs. faster
Monte-Carlo approach (suited for
high-statistics tracking studies).
• Benchmark of H8 data critical.
Overall good agreement.
• Benchmark of different routine used to validate
the scaling to 7 TeV.
A lot ongoing to improved our prediction
capability for the LHC case!
Plan to organize a workshop on that at
the beginning of 2014.
S. Redaelli, SPSC, 22-10-2013
D. Mirarchi, A. Taratin at al.
}
}
Taratin’s
routine
LHC predictions (implementation for tracking):
- Reviewed nuclear and electronic
dechanneling lengths.
- Improved scattering routine.
- Improving nuclear interaction cross sections
for paerticles in channeling.
SixTrack
routine
• Recent improvement of routine used for
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Status of proposal for LHC
•Converged on IR7 layouts for machine studies
in horizontal and vertical planes.
•Existing secondary collimators to be used as
absorbers during low-intensity MD’s only.
Worked out preliminary settings that optimize
cleaning of a crystal-based system.
•Identified locations of additional detectors.
•LHC engineering change request (ECR) under
approval with the following proposal:
• Cabling for complete experiment;
• Installation of 2 goniometers;
• Space reservations for detectors.
(nice to have but not essential for the initially
feasibility demostration)
•Plan an internal review at the end of the year to
address qualification of available hardware and
readiness within the tight LS1 schedule.
•Collected first ideas on controls and interlock
strategy for integration into the LHC system.
S. Redaelli, SPSC, 22-10-2013
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Conclusions
The main UA9 activities of the last year were reported.
- Almost no beam in the last year since SPSC2012
➙ focus on simulations, analysis, detector and goniometer technology.
The SPS apparatus has matured to a complete setup that addressed
various key points for the crystal-based collimation in accelerators.
- Single-pass setup in SPS-NA (+HRM) and multi-turn setup in the SPS.
- A list of key achievements was given: alignment, loss rate reduction, loss
maps, cleaning of dispersion areas.
New crystal robustness experiment in HiRadMat ➙ soon final results.
Recent results include a better understanding of crystal modelling and
a development of new detector concepts (under tests at FNL, Rome).
Important work on the definition of a crystal experiment at the LHC
- Produced layouts for low-intensity feasibility studies. ECR under approval.
It is crucial to continue with high priority the UA9 activities with SPS
beams to be well prepared for the LHC challenges.
S. Redaelli, SPSC, 22-10-2013
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