Transcript Cherenkov detector for proton Flux Measurement

Cherenkov detector for proton Flux
Measurement (CpFM) for UA9 experiment
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F. Iacoangeli, 1 D. Breton, 1 V. Chaumat, 3 G. Cavoto, 1 S. Conforti Di Lorenzo,
1 L. Burmistrov, 3 M. Garattini, 1 J. Jeglot, 1 J. Maalmi, 2 S. Montesano, 1 V. Puill, 2 R.Rossi,
2 W. Scandale, 1 A. Stocchi, 1 J-F Vagnucci
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LAL, Univ Paris-Sud, CNRS/IN2P3, Orsay, France
CERN - European Organization for Nuclear Research, CH-1211 Geneva 23, Switzerland
3 INFN - Roma La Sapienza, Italy
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Outline
• UA9 experiment at SPS
• LUA9 project
• CpFM detection chain components
• Optical simulations on the Cherenkov radiator
• Beam tests at BTF of simplified prototypes (October 2013)
• Beam test at BTF of the CpFM full chain (April 2014)
• First preliminary results of the beam test
• Conclusions
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UA9 experiments
 The main purpose of UA9 is to demonstrate the possibility of using a bent silica crystal
as primary collimator for hadron colliders .
 Bent crystal works as a “smart deflectors” on primary halo particles
θch ≅ αbending
amorphous
<θ>MCS≅3.6μrad @ 7 TeV
channeling
θoptimal @7TeV≅ 40 μrad
R. W. Assmann, S. Redaelli, W. Scandale,
“Optics study for a possible crystal-based
collimation system for the LHC”, EPAC
06c
UA9 experiment runs in SPS since 2009
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Crystal assisted collimation
 If the crystalline planes are correctly oriented, the particles are subject to a
coherent interaction with crystal structure (channeling).
 This effect impart large deflection which allows to localize the losses on a single
absorber and reduces the probability of diffractive events and ion fragmentation
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LUA9 project
Use bent crystal at LHC as a primary collimator
LHC beam pipe (primary vacuum)
To monitor the secondary beam a Cherenkov detector, based on quartz radiator, can be used.
Aim: count the number of protons with a precision of about 5% (in case of 100 incoming
protons) in the LHC environment so as to monitor the secondary channelized beam.
Main constrains for such device:
- No degassing materials (inside the primary vacuum).
- Radiation hardness of the detection chain (very hostile radioactive environment).
- Compact radiator inside the beam pipe (small place available)
- Readout electronics at 300 m
 Cherenkov detector for proton Flux Measurements (CpFM) 5
CpFM detection chain components
Radiation hard quartz (Fused Silica)
radiator
Flange with custom viewport to realize
UHV seal and optical air/vacuum
interface
Movable bellow
Quartz/quartz (core/cladding)
radiation hard fibers.
USB-WaveCatcher read electronics. For more details see :
USING ULTRA FAST ANALOG MEMORIES FOR FAST PHOTO-DETECTOR READOUT (D. Breton et al. PhotoDet 2012, LAL Orsay)
The Cherenkov light will propagate inside the radiator and will be transmitted to the PMT
throughout the bundle of optical fibers. Radiator must work as waveguide.
The first prototype of CpFM will be installed and tested in SPS
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Geant 4 Optical Simulation
- We performed many simulation of the optical behavior of detection chain to define the
best configuration
Different reflection coefficient
At the end of detection chain
Angle wrt the fiber axis
At the radiator surface
The number of p.e. is strongly
dependent on reflection coefficient
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BTF Test Setup (October 2013)
LAL Cerenkov
INFN Cerenkov
e- Beam
BTF Remote
Control Table
BTF Calorimeter
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Radiator with fibers bundle
Charge per Electron
(normalized to electron path length into the radiator)
47°
Optical grease
at interfaces
between fibers,
PMT and radiator
The width of the peak is
compatible with the angular
aperture of the fibers
Radiator/beam angle
We need the light arrive to the
fibers with a angle compatible
with angular acceptance
The best geometry is with the radiator
which cross the beam with 47° angle and
the fibers coupled with the same angle so as
to use all the angular acceptance of fibers
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Best configuration for CpFM
Beam
 Radiator cross the beam perpendicularly,
due to small place available
 Fibers are coupled with 43° angle, so as
the incoming light is at 47° angle
Fibers
Quartz
̴ 43˚
 Flange brazed configuration
or
commercial viewport configuration
 “I” shape or “L” shape, so as to increase the quartz crossed by beam
The “double bar” configuration will be useful to measure the
diffusion of the beam and the background
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New BTF Set-up of CpFM (April 2014)
4 Cherenkov bars
(L and I shape)
47º end of the bars
MCP-PMT
Fibers bundle
PMTs
black boxes
Fibers bundle
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CpFM Test Setup @ BTF (April 2014)
The setup was almost the same of last test beam , except for the long fibers bundle
and for the readout provided by WaveCatcher board.
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Tested configurations
• Configuration A : Trioptics Quartz bars (L curved bars) + bundle + PMT
• Configuration B : Optico AG L + I bars + bundle + PMT
• Configuration C: I bar + PMT (direct coupling)
• Configuration D: I bar + glass plate (thickness=3,85 mm) +PMT
• Configuration E: I bar + glass plate (thickness=3,85 mm) +bundle + PMT
(simulation of a viewport)
• Configuration F : quartz I bar with a black tape around it + bundle + PMT
(simulation of an absorber around the bar)
• Configuration G : bundle in the beam For all these configurations,
The signal is recorded by the WaveCatcher 8 channels module
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“L” and “I” bars + bundle + PMTs (R7378A)
“L” yield less signal than “I”
“ I ” bar configuration
• Higher light signal, due to a better
surface polishing
• Number of detected p.e. quite linear
“ L” bar configuration
• Lower light signal, due to a worst
surface polishing
• Detected p.e. increase when beam
came near to the fiber bundle
• In principle more light produced in
the 3 cm fused silica along the beam
direction (“L” shorter arm)
The polishing, difficult because of the “L”
shape, must be enhanced. Reflectivity is
essential feature of radiator
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Optical AG Fused Silica bars
Well polished “I” bar:
it is possible to distinguish
the reflection points along
the bar
Worse polished “L” bar:
the light appears more
widespread and only few
reflection points are visible
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Mounting configurations
 Another result was obtained by the study of mounting with viewport
At the start we proposed 2 different mounting configuration
Flange brazed
configuration
• Better light transport (no
viewport interfaces)
• Better mechanical strength
• Loss of light in the brazed
points
• Technological problems to
braze Fused Silica with iron
flange
Viewport
configuration
• Worst light transport
(viewport interfaces)
• More complex mechanical
set-up
• No technological problems
The brazed flange is still under
development
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Effect of the viewport
Configuration:“I” bar + quartz plate+ bundle + PMT
- CpFM output with viewport= 1.2 p.e/
incident electron
- Signal per e- ( @ 800 kV) :
• without window: 10.5 mV
• With window: 6.0 mV
Few-particles
regime (<4 e-)
-
Reduction of the signal is about 40 %
The insertion of a quartz plate (thickness = 3.85mm) between the quartz output and the
fibers bundle decreases the signal by a factor less than 2
The CpFM with viewport is a suitable solution
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CpFM and BTF Calorimeter correlation
Few-particles
regime (<4 e-)
The study of measured CpFM charge (normalized on the charge of single p.e.) as a
function of BTF calorimeter charge shows a rather linear dependence.
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Conclusions
• We have evidence that the full chain (radiator + quartz window + fiber bundle + PMTs)
works well, also for low fluxes
• We need more time to finish analysis of the data. All the measurements need to be
compared with simulations as well
• We chose the “I” shape bars and the mounting with viewport for the first CpFM
• The obtained signal is ~1 p.e. per incident e-. It can be improved by a factor 5 or 6 by
means of very well polished L bars (not yet available).
• The brazing of the quartz bars with a flange needs of a long collaboration process with a
specialized company. It’s not possible for the installation of the CpFM in SPS this winter but
it has to be done for the future (LHC)
• We have measured 250 ps of time spread for the best timing configuration of CpFM. This
features can be improved using a faster readout electronics.
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Thank you for attention
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SPARE
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Channeling effect of the charged
particles in the bent crystal
Mechanically bent crystal
Using of a secondary
curvature of the crystal to
guide the particles
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Multi stage collimation as in LHC

The halo particles are removed by a cascade of amorphous targets:
1.
Primary and secondary collimators intercept the diffusive primary halo.
2.
Particles are repeatedly deflected by Multiple Coulomb Scattering also producing hadronic
showers that is the secondary halo
3.
Particles are finally stopped in the absorber
4.
Masks protect the sensitive devices from tertiary halo
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beam core

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6.2
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tertiary halo
& showers
masks
secondary
collimator
1m CFC
secondary
collimator
1m CFC
secondary halo
& showers
tertiary
collimator
absorber 1m W
secondary halo
& showers
Sensitive
devices
(ARC, IR
QUADS..)
>10
Normalizes
aperture [σ]
primary collimator
0.6 m CFC
primary halo
Collimation efficiency in LHC ≅ 99.98% @ 3.5 TeV

Probably not enough in view of a luminosity upgrade

Basic limitation of the amorphous collimation system
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Loss rate along the SPS ring
Loss map measurement in 2011: intensity increased
from 1 bunch (I = 1.15 x 1011 p) to 48 bunches, clear
reduction of the losses seen in Sextant 6.

Loss map measurement in 2012: maximum possible
intensity: 3.3 x 1013 protons (4 x 72 bunches with 25
ns spacing), average loss reduction in the entire ring !
2011 data
protons
Reduction factor (Lam / Lch)

2012 data
protons (270 GeV)
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The Wave Catcher board
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Results of the simulations without fibers
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CpFM detection chain components
 Fused Silica HPFS 7980
(M. Hoek , “Radiation Hardness Study on Fused Silica”. RICH 2007)
 Fibers with core and cladding made of fused silica
(U. Akgun et al., "Quartz Plate Calorimeter as SLHC Upgrade to CMS Hadronic
Endcap Calorimeters", CALOR 2008)
 Hamamatsu R672 & R7378A
(A. Sbrizzi LUCID in ATLAS )
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Time resolution
- Time resolution measurements were performed with multi-particles events (Ne=236) so as to have at least
1 particles in the first microbunch.
RMS=266ps
Ne=236
RMS=455ps
10 ns
We don’t know the cause of
the 2 distinct distributions
20 ns
-We measure the delay from trigger edge (LINAC NIM Timing signal) of the first particle of
each event
- The CpFM take out a distribution similar to the CALO’s one but by far less light
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I bar with + bundle + PMT1 last run 235
(low flux)
Online analysis
Preliminary
Preliminary
We have a signal even in the single-particle regime
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