The LHCb VELO detector – an application of a Silicon Strip detector

1. The LHCb VELO detector –anapplication of a Silicon Strip detector Tomasz Cybulski University of Liverpool , UK The Cockcroft Institute, UK t.cybulski@liv.ac.uk

2. Outline IntRo QCT QCMA SDP LVA LVE Sum • Intoroduction to radiotherapy • Quality Control Teaser • Quality Control for Medical Accelerator • Semiconductor Detection Principles • LHCbVELO Architecture • LHCbVELO Electronics • Summary 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

3. Introduction to Radiotherapy Fig. 2. Single strand DNA brake. [2] IntRo QCT QCMA SDP LVA LVE Sum - X – ray photon Fig. 1. Principles of conformal radiotherapy. [1] Fig. 3. Double strand DNA brake. [2] 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

4. Introduction to Radiotherapy IntRo QCT QCMA SDP LVA LVE Sum Fig. 4. Dose depth distribution for different types of radiation. [3] 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

5. Introduction to Radiotherapy IntRo QCT QCMA SDP LVA LVE Sum Fig. 5. Energy deposition by proton beam as a function of depth - Bragg peak. [4] Fig. 6. Sagittal colour-wash dose display for the treatment on meduloblastoma. [4] 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

6. Introduction to radiotherapy IntRo QCT QCMA SDP LVA LVE Sum E1 E2  E3 • Parameters determining the quality and effectiveness of radiotherapy treatment: • 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 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

7. AQuality ControlTeaser IntRo QCT QCMA SDP LVA LVE Sum Fig. 9. Beam halo hit map on the LHCb VELO at the distance d = 110mm from the collimator. [5] 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] 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

8. Quality Control for Medical Accelerator IntRo QCT QCMA SDP LVA LVE Sum Fig. 11. Treatment room set up at Clatterbridge Centre for Oncology. [3] 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

9. Silicon DetecTor Principles IntRo QCT QCMA SDP LVA LVE Sum Charge movement in semiconductors Diffusion Drift in electric field – mobility in Si (77K) 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

10. StripSiliconDetector IntRo QCT QCMA SDP LVA LVE Sum Fig. 13. Cluster shapes for a underdepleted and fully depleted silicon strip detector. [6] Fig. 14. TDR LHCb VELO detector sensor structure. [6] 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

11. LHCb VELO Architecture LHCbVErtexLOcator (VELO) – reconstruction of vertices tracks of decays of beauty- and charm- hadrons in LHCb experiment. IntRo QCT QCMA SDP LVA LVE Sum Detector design and construction requirements: Performance Geometrical Environmental Machine integration Fig. 15.LHCb VELO modules in cross section in LHCb experiment. [7] 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

12. LHCb VELO Architecture 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 IntRo QCT QCMA SDP LVA LVE Sum 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

13. LHCb VELO Architecture 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 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 1014neq / cm2 IntRo QCT QCMA SDP LVA LVE Sum 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

14. LHCb VELO Architecture Tab. LHCb VELO sensors parameters IntRo QCT QCMA SDP LVA LVE Sum φ – sensor strip pitch Fig. 16. rφ geometry of the LHCb VELO sensors (n-on-n). R – sensor strip pitch 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

15. LHCb VELO Architecture IntRo QCT QCMA SDP LVA LVE Sum Fig. 17. Layout of the LHCb VELO module. [7] 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

16. LHCb VELO electronics IntRo QCT QCMA SDP LVA LVE Sum Fig. 18.LHCb VELO readout electronics. [7] 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

17. LHCb VELO electronics Beetle chip CMOS technology, 0.12 µm, radiation hard ASIC, analogue IntRo QCT QCMA SDP LVA LVE Sum Noise Equivalent Charge ENC = 790e +17.5e /pF Fig. 19. Beetle chip architecture and pulse shape. The Spill over has to be lower than 0.3 of the peak value after 25ns.[8] The Response of the Beetle to the test-pulse: the measuredrisetimeis 14.7 +/- 0.5 ns and the spillover (26 +/- 0.6%). 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

18. LHCb VELO electronics Repeater Boards Functions: Repeater for differential signals Time Fast Control Beetle Chips configuration signals Carrier of voltage regulators for Beetle Chips and L0 electronics service systems ECS card: repeats the signals for the I2C configurationbus and controls and monitors the LV regulators IntRo QCT QCMA SDP LVA LVE Sum 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

19. LHCb VELO electronics TELL 1 cards for VELO Functions: Digitization of the data – 10 bit digitizers sample at the frequency of 40 MHz: 4 A-Rx cards, 16 channels each card Pedestal subtraction IntRo 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] 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

20. LHCb VELO electronics Cross – talk removal Channel re-ordering Common mode suppression Clustering – up to fourstrips: seedingtreshold, inclusiontresholdcut. IntRo QCT QCMA SDP LVA LVE Sum Fig. 21. ADC noise before and after channel reordering in Phi – sensor. [9] Fig. 22. Common noise suppression for signal from each Beetle Chip. 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

21. LHCb VELO electronics Summary Proof of principle measurements indicate that the LHCb VELO is capabletomeasure proton beams It seems possible to qualitatively estimate the proton beam halodivergenceby use of the VELO detector Further studies will investigate into potential correlations between beamcurrent and halo signal The possible use of the VELO detector as a non-invasive method for beamQCwill be assessed IntRo QCT QCMA SDP LVA LVE Sum 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011

22. Any questions? Thank you 6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011