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The LHCb VELO detector – an application of a Silicon Strip detector
Tomasz Cybulski University of Liverpool , UK The Cockcroft Institute, UK
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Outline Intoroduction to radiotherapy Quality Control Teaser
Quality Control for Medical Accelerator Semiconductor Detection Principles LHCb VELO Architecture LHCb VELO Electronics Summary IntRo QCT QCMA SDP LVA LVE Sum 6th DITANET Topical Workshop on Particle Detection Techniques - Seville
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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
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Introduction to Radiotherapy
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
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Introduction to Radiotherapy
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
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Introduction to radiotherapy
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
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A Quality Control Teaser
IntRo QCT QCMA SDP LVA LVE Sum Fig. 9. Beam halo hit map on the LHCb VELO at the distance d = 110 mm 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
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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
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Silicon DetecTor Principles
IntRo QCT QCMA SDP LVA LVE Sum Charge movement in semiconductors Diffusion Drift in electric field 𝜗 ℎ = 𝜇 ℎ ∙𝜀 𝜗 𝑒 = 𝜇 𝑒 ∙𝜀 𝜎= 2𝑘𝑇𝑥 𝑒𝜀 𝜎 ≤100𝜇𝑚 𝜇 – mobility in Si (77K) 𝜇 𝑒 =2.1 ∙ 𝑐𝑚 2 /𝑉𝑠 𝜇 ℎ =1.1 ∙ 𝑐𝑚 2 /𝑉𝑠 6th DITANET Topical Workshop on Particle Detection Techniques - Seville
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Strip Silicon Detector
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
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LHCb VELO Architecture
LHCb VErtex LOcator (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
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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
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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 1014 neq / cm2 IntRo QCT QCMA SDP LVA LVE Sum 6th DITANET Topical Workshop on Particle Detection Techniques - Seville
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Fig. 16. rφ geometry of the LHCb VELO sensors
LHCb VELO Architecture Tab. LHCb VELO sensors parameters IntRo QCT QCMA SDP LVA LVE Sum Fig. 16. rφ geometry of the LHCb VELO sensors (n-on-n). φ – sensor strip pitch R – sensor strip pitch − 𝑟− −8170 −40 𝑟 − −8190 − 𝑟 − −17250 6th DITANET Topical Workshop on Particle Detection Techniques - Seville
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Fig. 17. Layout of the LHCb VELO module. [7]
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
![Fig. 17. Layout of the LHCb VELO module. [7]](http://slideplayer.com/slide/12397236/74/images/15/Fig.+17.+Layout+of+the+LHCb+VELO+module.+%5B7%5D.jpg "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")
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Fig. 18. LHCb VELO readout electronics. [7]
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
![Fig. 18. LHCb VELO readout electronics. [7]](http://slideplayer.com/slide/12397236/74/images/16/Fig.+18.+LHCb+VELO+readout+electronics.+%5B7%5D.jpg "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")
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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 measured rise time is /- 0.5 ns and the spillover (26 +/- 0.6%). 6th DITANET Topical Workshop on Particle Detection Techniques - Seville
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LHCb VELO electronics Repeater Boards Functions: IntRo
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 configuration bus and controls and monitors the LV regulators IntRo QCT QCMA SDP LVA LVE Sum 6th DITANET Topical Workshop on Particle Detection Techniques - Seville
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LHCb VELO electronics TELL 1 cards for VELO Functions: IntRo
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
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LHCb VELO electronics Cross – talk removal Channel re-ordering IntRo
Common mode suppression Clustering – up to four strips: seeding treshold, inclusion treshold cut. 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
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LHCb VELO electronics Summary
Proof of principle measurements indicate that the LHCb VELO is capable to measure proton beams It seems possible to qualitatively estimate the proton beam halo divergence by use of the VELO detector Further studies will investigate into potential correlations between beam current and halo signal The possible use of the VELO detector as a non-invasive method for beam QC will be assessed IntRo QCT QCMA SDP LVA LVE Sum 6th DITANET Topical Workshop on Particle Detection Techniques - Seville
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Thank you Any questions?
6th DITANET Topical Workshop on Particle Detection Techniques - Seville
