Use of Silicon Detectors for Proton Diagnostics Tomasz Cybulski

Outline Scanditronix MC-60 Cyclotron at CCC Beam Dynamics LHCb VELO detector Measurement method Faraday Cup optimisation Experiment Outlook PASI Workshop - RAL,

S CANDITRONIX MC-60 PF CYCLOTRON Fig. 1. Technical drawings of the Scanditronix MC-60 PF Cyclotron unit at Clatterbridge Cancer Centre (CCC), Wirral, UK. [5] PASI Workshop - RAL, Fig. 2. Scanditronix MC-60 PF cyclotron at CCC.

S CANDITRONIX MC-60 PF CYCLOTRON Fig. 3. Cyclotron accelerating cavities and acceleration principle. [] PASI Workshop - RAL, Tab. 2. Treatment beam parameters.

PASI Workshop - RAL, M EASUREMENT METHOD Fig. 4. Proof of principle measurements, where ‘halo’ beam divergence was demonstrated.

M EASUREMENT M ETHOD PASI Workshop - RAL, Fig. 5. Treatment beam line at Clatterbridge Cancer Centre.

C LATTERBRIDGE B EAM D YNAMICS Q1Q2Q3 Fig. 6. Beam dynamics simulation studies in the beam line at CCC. PASI Workshop - RAL,

C LATTERBRIDGE B EAM D YNAMICS l – drift length Beam waist Beam line Quadrupole Focusing plane Defocusing plane Drift space Fig. 7. Beam line transport through optical elements.

PASI Workshop - RAL, C LATTERBRIDGE B EAM D YNAMICS Fig. 7. Experimental setup at CCC. Fig. 8. Reference image of the scintillating screen.

PASI Workshop - RAL, C LATTERBRIDGE B EAM D YNAMICS Fig. 9. Quadrupole scan for different QUAD 1 parameters.

PASI Workshop - RAL, Quasar Group - Project update C LATTERBRIDGE B EAM D YNAMICS Fringe fields approach: In formulation of the transport through the quadrupole magnet it is assumed the function is a step function. R – bore apperture

C LATTERBRIDGE B EAM D YNAMICS Q1Q2Q3 Fig. 10. Beam dynamics simulation studies in the beam line at CCC – Oleg Karamyshev. PASI Workshop - RAL, Q3Q2

LHCb VErtex LOcator (VELO) – reconstruction of vertices tracks of decays of beauty- and charm- hadrons in LHCb experiment. Fig. 11. LHCb VELO modules in cross section in LHCb experiment. [1] Detector design and construction requirements: Performance Geometrical Environmental Machine integration PASI Workshop - RAL, LHC B VELO DETECTOR

DETECTOR REQUIREMENTS Performance: Signal to noise ratio: S/N aimed to be greater than 14 to ensure efficient trigger performance Efficiency: the overall channel efficiency at least 99% for a signal to noise ratio cut S/N > 5 Resolution: a spatial cluster resolution of about 4 µm for tracks 100mrad in the region with the pitch region for 40 µm Spill over probability: fraction of the peak signal remaining after 25ns shall be less than 0.3 to keep the number of remnant hits at the level acceptable for the HLT PASI Workshop - RAL, LHC B VELO DETECTOR

DETECTOR REQUIREMENTS Geometrical: Polar angle acceptance: down to 15 mrad for all events with a primary vertex within ± 2σ of the nominal reaction point with no more than 8mm distance from the beam The track angular acceptance: a track of angular acceptance of 300 mrad should cross at least 3 VELO modules Fig. 12. LHCb VELO modules in cross section in LHCb experiment. [1] PASI Workshop - RAL, LHC B VELO DETECTOR

Performance: Covering full azimuthal acceptance Environmental: Sustain 3 years of nominal LHCb operation: damage to silicon in the inner region for one year should stand the irradiation of 1MeV neutrons with a flux of 1.3 x n eq / cm 2 Fig. 13. rφ geometry of the LHCb VELO sensors (n-on-n). Fig. 13. rφ geometry of the LHCb VELO sensors (n-on-n). PASI Workshop - RAL, LHC B VELO DETECTOR

Fig. 14. rφ geometry of the LHCb VELO sensors (n-on-n). Fig. 14. rφ geometry of the LHCb VELO sensors (n-on-n). Tab. 4. LHCb VELO sensors parameters R – sensor strip pitch φ – sensor strip pitch PASI Workshop - RAL, LHC B VELO DETECTOR

Advantages: Uniformity of capacitance per channel Execution time of track reconstruction Fig.. R - sensor optimisation. PASI Workshop - RAL, LHC B VELO DETECTOR Number of clone ghost tracks

PASI Workshop - RAL, LHC B VELO DETECTOR Fig. 12. VELO sensor signal creation. Diffusion Charge movement in semiconductors Drift in electric field

Beetle chip CMOS technology, 0.12 µm, radiation hard ASIC, analogue Fig. 17. Beetle chip architecture and pulse shape. The Spill over has to be lower than 0.3 of the peak value after 25ns.[2] The Response of the Beetle to the test-pulse: the measured rise time is /- 0.5 ns and the spill-over (26 +/- 0.6%). Noise Equivalent Charge ENC = 790e +17.5e /pF PASI Workshop - RAL, LHC B VELO DETECTOR Spill over probability: fraction of the peak signal remaining after 25ns shall be less than 0.3 to keep the number of remnant hits at the level acceptable for the HLT

PASI Workshop - RAL, LHC B VELO DETECTOR Fig. 18. LHCb VELO detector hybrid layout.

Fig. 19. LHCb VELO readout electronics. [1] PASI Workshop - RAL, LHC B VELO DETECTOR

TELL 1 cards for VELO Functions: 1.Digitization of the data – 10 bit digitizers sample at the frequency of 40 MHz: 4 A-Rx cards, 16 channels each card TELL 1 cards for VELO Functions: 1.Digitization of the data – 10 bit digitizers sample at the frequency of 40 MHz: 4 A-Rx cards, 16 channels each card PASI Workshop - RAL, LHC B VELO DETECTOR Fig. 23. Signal from r - and phi-sensor.

TELL 1 cards for VELO 2.Pedestal subtraction Fig.24. Pedestal subtraction from the signal determined for two chips. The ADC count corresponds to the charge of approx. 450 electrons, thus the signal is of about 50 ADC counts. The noise is of about 2 – 3 ADC counts. [9] PASI Workshop - RAL, LHC B VELO DETECTOR

TELL 1 cards for VELO 3.Cross – talk removal 4.Channel re-ordering Fig. 25. ADC noise before and after channel reordering in Phi – sensor. [9] PASI Workshop - RAL, LHC B VELO DETECTOR

TELL 1 cards for VELO 5.Common mode suppression 6.Clustering – up to four strips: seeding threshold, inclusion threshold cut. Fig. 26. Common noise suppression for signal from each Beetle Chip. PASI Workshop - RAL, LHC B VELO DETECTOR

Signal formation in silicon sensor of LHCb VELO detector: Inhomogeneous charge distribution along the particle track The emission of δ-rays (secondary electrons) Diffusion during charge collection Capacitive charge coupling between strips Spill-over PASI Workshop - RAL, LHC B VELO DETECTOR

Geometrical parameters determining the particle trajectory: 1.Cluster position – best estimate of position in the centre plane of the silicon. 2.Projected angle – estimate of the uncertainty of the cluster position PASI Workshop - RAL, LHC B VELO DETECTOR

3. Weighting of the charge sharing inside silicon assumes a linear relation between inter – strip impact position and the signal measured on adjacent strips – never the case! (No advanced algorithm has been developed so far). PASI Workshop - RAL, LHC B VELO DETECTOR

PASI Workshop - RAL, F ARADAY C UP OPTIMISATION Fig. 20. Faraday Cup region arrangement for optimisation studies. Faraday Cup optimisation summary – estimated currents: 1.Electrons 2.Protons 3.Positrons 4.He - 4

PASI Workshop - RAL, F ARADAY C UP OPTIMISATION Material and geometry optimisation summary: PROTONSELECTRONS

PASI Workshop - RAL, F ARADAY C UP OPTIMISATION Fig. 21. Electron current estimation for electrons leaving the Aluminium target material.

PASI Workshop - RAL, M EASUREMENT METHOD – STAND ALONE SET UP Fig. 29. Faraday Cup design layout. Faraday Cup impedance matching

PASI Workshop - RAL, M EASUREMENT METHOD – STAND ALONE SET UP Fig. 23. LHCb VELO integration with the CCC treatment beam line. Fig. 14. Heat distribution with out and with 40W cooling of the detector.

PASI Workshop - RAL, E XPERIMENT - DATAFLOW Faraday Cup LabVIEW interface data acq & saving GaGe RAZOR digitizer card TRIGGER POSITION LHCb VELO

PASI Workshop - RAL, E XPERIMENT - DATAFLOW

PASI Workshop - RAL, OUTLOOK 1.Performance tests 2.Data analysis 3.FURTHER GOALS - Optimisation of the LHCb VELO detector for medical proton machines 1.Performance tests 2.Data analysis 3.FURTHER GOALS - Optimisation of the LHCb VELO detector for medical proton machines

Thank you Any questions? Thank you PASI Workshop - RAL,