First BTF Users Workshop 6-7 May Laboratori Nazionali di Frascati Marco Garattini on behalf of the UA9 Cherenkov detector team 3 M. Garattini, 1 D. Breton, 1 V. Chaumat, 3 G. Cavoto, 1 S. Conforti Di Lorenzo, 1 L. Burmistrov, 3 F. Iacoangeli, 1 J. Jeglot, 2 F. Loprete, 1 J. Maalmi, 2 S. Montesano, 1 V. Puill, 2 W. Scandale, 1 A. Stocchi, 1 J-F Vagnucci 1 LAL, Univ Paris-Sud, CNRS/IN2P3, Orsay, France 2 CERN - European Organization for Nuclear Research, CH-1211 Geneva 23, Switzerland 3 INFN - Roma La Sapienza, Italy “BTF Test of Cherenkov detector for proton Flux Measurement (CpFM)”

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

Crystal assisted collimation  Bent crystals work as a “smart deflectors” on primary halo particles  Coherent particle-crystal interactions impart large deflection angle that minimize the escaping particle rate and improve the collimation efficiency Silicon bent crystal Normalizes aperture [σ] > beam core primary halo secondary halo & showers primary collimator 0.6 m CFC secondary collimator 1m CFC secondary collimator 1m CFC absorber 1m W Sensitive devices (ARC, IR QUADS..) masks Deflected halo beam Multiple Coulomb scattered halo (multi-turn halo) Dechanneled particles in the crystal volume Collimators partially retracted Absorber retracted channelingamorphous θ ch ≅ α bending MCS ≅ 7 TeV θ ≅ 40 μ rad R. W. Assmann, S. Redaelli, W. Scandale, “Optics study for a possible crystal-based collimation system for the LHC”, EPAC 06c

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. 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)

CpFM detection chain components Radiation hard quartz (Fused Silica) radiator The flange with view port attached to the movable bellow The light will propagate inside the radiator and will then be transmitted to the PMT via a bundle of optical fibers Quartz/quartz (core/cladding) radiation hard fibers. 300 m cable USB-WC electronics. For more details see : USING ULTRA FAST ANALOG MEMORIES FOR FAST PHOTO-DETECTOR READOUT (D. Breton et al. PhotoDet 2012, LAL Orsay)

Geant 4 Optical Simulation Different reflection coefficientAngle wrt the fiber axis At the end of the bar At the end of the CpFM chain

BTF Setup (October 2013) INFN Cerenkov LAL Cerenkov BTF Calorimeter e- Beam BTF Remote Control Table

Radiator with fibers bundle Radiator rotation angle Charge signal normalized to number of incident electron and electron path length in the radiator (arbitrary units) - 47º Optical grease at interfaces between fibers, PMT and radiator The width of the peak is compatible with the numerical aperture of the fibers

Best configuration for CpFM Quartz Fibers ̴ 43˚ Beam Viewport configurationFlange brazed configuration - L bar or - I bar The “double bar” configuration will be useful to measure the diffusion of the beam and the background

Geant 4 Optical Simulation Different reflection coefficientAngle wrt the fiber axis

New BTF Set-up of CpFM (April 2014) Fibers bundle MCP-PMT Cherenkov bars 47º end of the bars PMTs black boxes

Schedule for CpFM tests in BTF (April 2014) 1. CpFM alignment with the beam: X-Y scan Measurement in the range 50, 100, 300, 400, 500 e - for “I”, “L” bars: 2. Quartz + MCP-PMT : to check that we have a signal at the quartz output even with the curved shape and the interface with the false flange… 3. The CpFM: quartz + fibers bundle + PMTs + long low attenuation cables + WaveCatcher 4. Quartz + Viewport (or stack of glass plates) + MCP-PMT : to simulate an inclined viewport with different thickness 5. Bundle of fibers inside the beam: the background due to the bundle itself 6. Cross-talk between the 2 channels of the CpFM 7. Quartz + metallic rings of different widths to simulate the brazing thickness Measurement with 1 electron (low fluxes): 8. timing measurements

bundle “L” and “I” bars + bundle + PMTs (R7378A) “ I ” bar configuration Higher light signal, probably due to a better surface polishing In principle less light produced: less thickness “ L” bar configuration Lower light signal, probably due to a worst surface polishing In principle more light produced in the 3 cm fused silica along the beam direction (“L” shorter arm) “Optical AG” quartz bars Preliminary

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 the reflection points are not 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 metal alloys Viewport configuration Worst light transport (viewport interfaces) More complex set-up No technological problems “L” and “I” bars mm glass “window” + PMT2 (BA1512) Without window: With window: 10.5 (800 kV) 6.0 (800 kV) Reduction of the signal is about 40 %

I bar with + bundle + PMT1 last run 235 (low flux) Online analysis We have a signal even in the single-particle regime Preliminary

Conclusions We have evidence that the full chain (radiator + glass window + fiber bundle + PMTs) works well, also for low fluxes We need more time to finish analysis of the data (use charge instead of amplitude) All the measurements need to be compared with simulations as well We chose the “I” shape for the first CpFM (with viewport) Different solution for a better polished “L” shape bar but none is already available We are investigating some technological solution for the brazing of fused silica bars with metal alloys (i.e. KOVAR)

Thank you especially to the BTF and LINAC stuff…

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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

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 Normalizes aperture [σ] > beam core primary halo secondary halo & showers secondary halo & showers tertiary halo & showers primary collimator 0.6 m CFC secondary collimator 1m CFC secondary collimator 1m CFC tertiary collimator absorber 1m W Sensitive devices (ARC, IR QUADS..) masks  Collimation efficiency in LHC ≅ 3.5 TeV Probably not enough in view of a luminosity upgrade Basic limitation of the amorphous collimation system

Loss rate along the SPS ring  Loss map measurement in 2011: intensity increased from 1 bunch (I = 1.15 x p) to 48 bunches, clear reduction of the losses seen in Sextant 6.  Loss map measurement in 2012: maximum possible intensity: 3.3 x protons (4 x 72 bunches with 25 ns spacing), average loss reduction in the entire ring ! 2012 data protons (270 GeV) Reduction factor (L am / L ch ) 2011 data protons

Results of the simulations without fibers