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3 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 Vagnucci1 LAL, Univ Paris-Sud, CNRS/IN2P3, Orsay, France

2 CERN - European Organization for Nuclear Research, CH-1211 Geneva 23, Switzerland3 INFN - Roma La Sapienza, Italy

Cherenkov detector for proton Flux Measurement (CpFM) for UA9 experiment

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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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channelingamorphous

θch ≅ αbending

<θ>MCS≅3.6μrad @ 7 TeV

θoptimal @7TeV≅ 40 μradR. W. Assmann, S. Redaelli, W. Scandale, “Optics study for a possible crystal-based collimation system for the LHC”, EPAC 06c

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

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 projectUse 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 incomingprotons) 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)

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CpFM detection chain componentsRadiation hard quartz (Fused Silica) radiator

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 first prototype of CpFM will be installed and tested in SPS

Flange with custom viewport to realize UHV seal and optical air/vacuum interface

Movable bellow

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.

Quartz/quartz (core/cladding) radiation hard fibers.

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Geant 4 Optical Simulation

Different reflection coefficient Angle wrt the fiber axis

- We performed many simulation of the optical behavior of detection chain to define the best configuration

The number of p.e. is strongly dependent on reflection coefficient

At the end of detection chain At the radiator surface

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BTF Test Setup (October 2013)

INFN Cerenkov

LAL Cerenkov

BTF Calorimeter

e- Beam

BTF Remote Control Table

Radiator with fibers bundle

47°

Charge per Electron(normalized to electron path length into the radiator)

Radiator/beam angle

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The width of the peak is compatible with the angular aperture of the fibers

Optical grease at interfaces

between fibers, PMT and radiator

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

We need the light arrive to the fibers with a angle compatible with angular acceptance

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Best configuration for CpFM

QuartzFibers

43˚

Beam

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

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

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New BTF Set-up of CpFM (April 2014)

Fibers bundle

Fibers bundle

MCP-PMT

4 Cherenkov bars (L and I shape)

47º end of the bars

PMTs black boxes

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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)“ 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)

bundle The polishing, difficult because of the “L” shape, must be enhanced. Reflectivity is essential feature of radiator

“L” yield less signal than “I”

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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

Mounting configurations

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

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Another result was obtained by the study of mounting with viewport

At the start we proposed 2 different mounting configuration

The brazed flange is still under development

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Effect of the viewportConfiguration:“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

- Reduction of the signal is about 40 %

The CpFM with viewport is a suitable solution

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

Few-particles regime (<4 e-)

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CpFM and BTF Calorimeter correlation

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.

Few-particles regime (<4 e-)

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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 secondarycurvature 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 halo3. Particles are finally stopped in the absorber 4. Masks protect the sensitive devices from tertiary halo

Normalizes

aperture [σ]

0

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beam coreprimary halo

secondary halo& showers

secondary halo& showers

tertiary halo& showers

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Sensitive devices (ARC, IR QUADS..)

mas

ks

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 !

2012 dataprotons (270 GeV)

Redu

ctio

n fa

ctor

(L a

m /

L ch)

2011 dataprotons

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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

-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

We don’t know the cause of the 2 distinct distributions

Ne=236RMS=266ps

RMS=455ps

10 ns

20 ns

- Time resolution measurements were performed with multi-particles events (Ne=236) so as to have at least 1 particles in the first microbunch.

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I bar with + bundle + PMT1 last run 235(low flux)

Online analysis

We have a signal even in the single-particle regime

PreliminaryPreliminary