Tomasz Cybulski University of Liverpool UK The Cockcroft

Tomasz Cybulski University of Liverpool , UK The Cockcroft Institute, UK t. cybulski@liv. ac. uk

� Intoroduction to radiotherapy � Quality Control Teaser � Quality Control for Medical Accelerator � Semiconductor Detection Principles Int. Ro QCT QCMA SDP � LHCb VELO Architecture LVA � LHCb VELO Electronics LVE � Summary 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011 Sum

- X – ray photon Fig. 2. Single strand DNA brake. [2] Int. Ro QCT QCMA SDP LVA LVE Fig. 1. Principles of conformal radiotherapy. [1] Sum Fig. 3. Double strand DNA brake. [2] 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011

Int. Ro QCT QCMA SDP LVA LVE Sum Fig. 4. Dose depth distribution for different types of radiation. [3] 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011

Int. Ro QCT Fig. 5. Energy deposition by proton beam as a function of depth - Bragg peak. [4] QCMA SDP LVA LVE Sum Fig. 6. Sagittal colour-wash dose display for the treatment on meduloblastoma. [4] 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011

E 1 E 2 E 3 Parameters determining the quality and effectiveness of radiotherapy treatment: 1. DOSE – determines energy deposited in a target (tumour) volume – number of ionisation events Parameter of importance: Beam current 2. Tumour coverage – irradiation of tumour volume and protection of healthy tissue Penetration depth - determines distal tumour coverage Parameter of importance: Energy Lateral spread – determines accuracy of lateral irradiation accuracy 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011 Int. Ro QCT QCMA SDP LVA LVE Sum

Int. Ro QCT QCMA Fig. 9. Beam halo hit map on the LHCb VELO at the distance d = 110 mm from the collimator. [5] SDP LVA LVE Sum Fig. 8. LHCb VELO module at the Clatterbridge Centre for Oncology. [5] Fig. 10. Divergence of the beam halo as a function of distance from the collimator. [5] 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011

Int. Ro QCT QCMA SDP LVA LVE Sum Fig. 11. Treatment room set up at Clatterbridge Centre for Oncology. [3] 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011

Int. Ro QCT QCMA Charge movement in semiconductors Diffusion Drift in electric field 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011 SDP LVA LVE Sum

Int. Ro QCT QCMA SDP LVA LVE Sum Fig. 13. Cluster shapes for a underdepleted and fully depleted silicon strip detector. [6] 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011 Fig. 14. TDR LHCb VELO detector sensor structure. [6]

LHCb VErtex LOcator (VELO) – reconstruction of vertices tracks of decays of beauty- and charm- hadrons in LHCb experiment. Int. Ro QCT Detector design and construction requirements: Performance QCMA SDP Geometrical Environmental Machine integration LVA LVE Sum Fig. 15. LHCb VELO modules in cross section in LHCb experiment. [7] 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011

DETECTOR REQUIREMENTS Performance: Signal to noise ratio: S/N aimed to be greater than 14 to ensure efficient trigger performance Int. Ro QCT QCMA Efficiency: the overall channel efficiency at least 99% for a signal to noise ratio cut S/N > 5 SDP Resolution: a spatial cluster resolution of about 4 µm for tracks 100 mrad in the region with the pitch region for 40 µm LVA Spill over probability: fraction of the peak signal remaining after 25 ns shall be less than 0. 3 to keep the number of remnant hits at the level acceptable for the HLT 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011 LVE Sum

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 8 mm distance from the beam Int. Ro QCT QCMA The track angular acceptance: a track of angular acceptance of 300 mrad should cross at least 3 VELO modules SDP Covering full azimuthal acceptance LVA Environmental: Sustain 3 years of nominal LHCb operation: damage to silicon in the inner region for one year should stand the irradiation of 1 Me. V neutrons with a flux of 1. 3 x 1014 neq / cm 2 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011 LVE Sum

Tab. LHCb VELO sensors parameters Int. Ro QCT QCMA SDP LVA φ – sensor strip pitch Fig. 16. rφ geometry of the LHCb VELO sensors (n-on-n). R – sensor strip pitch 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011 LVE Sum

Int. Ro QCT QCMA SDP LVA LVE Fig. 17. Layout of the LHCb VELO module. [7] 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011 Sum

Int. Ro QCT QCMA SDP LVA LVE Sum Fig. 18. LHCb VELO readout electronics. [7] 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011

Beetle chip Int. Ro CMOS technology, 0. 12 µm, radiation hard ASIC, analogue Noise Equivalent Charge ENC = 790 e +17. 5 e /p. F QCT QCMA SDP LVA LVE Fig. 19. Beetle chip architecture and pulse shape. The Spill over has to be lower than 0. 3 of the peak value after 25 ns. [8] The Response of the Beetle to the test-pulse: the measured rise time is 14. 7 +/- 0. 5 ns and the spillover (26 +/- 0. 6%). 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011 Sum

Repeater Boards Functions: 1. Repeater for differential signals 2. Time Fast Control Int. Ro QCT QCMA 3. Beetle Chips configuration signals SDP 4. Carrier of voltage regulators for Beetle Chips and L 0 electronics service systems LVA 5. ECS card: repeats the signals for the I 2 C configuration bus and controls and monitors the LV regulators LVE Sum 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011

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 2. Pedestal subtraction Int. Ro QCT QCMA SDP LVA LVE Sum Fig. 20. 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] 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011

2. Cross – talk removal 3. Channel re-ordering Int. Ro QCT Fig. 21. ADC noise before and after channel reordering in Phi – sensor. [9] 4. Common mode suppression QCMA SDP LVA LVE Sum Fig. 22. Common noise suppression for signal from each Beetle Chip. 5. Clustering – up to four strips: seeding treshold, inclusion treshold cut. 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011

Summary 1. Proof of principle measurements indicate that the LHCb VELO is capable to measure proton beams 2. It seems possible to qualitatively estimate the proton beam halo divergence by use of the VELO detector Int. Ro QCT QCMA 3. Further studies will investigate into potential correlations between beam current and halo signal SDP 4. The possible use of the VELO detector as a non-invasive method for beam QC will be assessed LVA LVE Sum 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011

Any questions? Thank you 6 th DITANET Topical Workshop on Particle Detection Techniques - Seville 08. 11. 2011