Tomasz Cybulski
University of Liverpool , UK
The Cockcroft Institute, UK
[email protected]
 Intoroduction
to radiotherapy
 Quality
Control Teaser
 Quality
Control for Medical Accelerator
 Semiconductor
Detection Principles
IntRo
QCT
QCMA
SDP
 LHCb
VELO Architecture
LVA
 LHCb
VELO Electronics
LVE
 Summary
6th DITANET Topical Workshop on Particle Detection
Techniques - Seville 08.11.2011
Sum
- X – ray photon
Fig. 2. Single strand DNA
brake. [2]
IntRo
QCT
QCMA
SDP
LVA
LVE
Fig. 1. Principles of conformal radiotherapy.
[1]
Sum
Fig. 3. Double strand DNA
brake. [2]
6th DITANET Topical Workshop on Particle Detection
Techniques - Seville 08.11.2011
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
IntRo
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]
6th DITANET Topical Workshop on Particle Detection
Techniques - Seville 08.11.2011
E1

E2  E3
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
6th DITANET Topical Workshop on Particle Detection
Techniques - Seville 08.11.2011
IntRo
QCT
QCMA
SDP
LVA
LVE
Sum
IntRo
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]
6th DITANET Topical Workshop on Particle Detection Techniques - Seville 08.11.2011
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
IntRo
QCT
QCMA
Charge movement in semiconductors
Diffusion
Drift in electric
field
𝜗ℎ = 𝜇ℎ ∙ 𝜀
𝜎=
2𝑘𝑇𝑥
𝑒𝜀
𝜗𝑒 = 𝜇𝑒 ∙ 𝜀
𝜎 ≤ 100𝜇𝑚
𝜇 – mobility in Si (77K)
𝜇𝑒 = 2.1 ∙ 104 𝑐𝑚2 /𝑉𝑠
𝜇ℎ = 1.1 ∙ 104 𝑐𝑚2 /𝑉𝑠
6th DITANET Topical Workshop on Particle Detection
Techniques - Seville 08.11.2011
SDP
LVA
LVE
Sum
IntRo
QCT
QCMA
SDP
LVA
LVE
Sum
Fig. 13. Cluster shapes for a underdepleted and
fully depleted silicon strip detector. [6]
6th 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.
IntRo
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]
6th 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
IntRo
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
100mrad in the region with the pitch region for 40 µm
LVA
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
6th 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 8mm distance from the beam
IntRo
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 1MeV neutrons
with a flux of 1.3 x 1014 neq / cm2
6th DITANET Topical Workshop on Particle Detection
Techniques - Seville 08.11.2011
LVE
Sum
Tab. LHCb VELO sensors parameters
IntRo
QCT
QCMA
SDP
LVA
Fig. 16. rφ geometry of the LHCb VELO sensors
(n-on-n).
R – sensor strip pitch
40 + 101.6 − 40
φ – sensor strip pitch
37.7 + 79.5 − 37.7
𝑟 − 8170
17250 − 8170
37.7 + 79.5 − 37.7
𝑟 − 17250
42000 − 17250
𝑟 −8190
41949 −8190
6th DITANET Topical Workshop on Particle Detection
Techniques - Seville 08.11.2011
LVE
Sum
IntRo
QCT
QCMA
SDP
LVA
LVE
Fig. 17. Layout of the LHCb VELO module. [7]
6th DITANET Topical Workshop on Particle Detection
Techniques - Seville 08.11.2011
Sum
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
Beetle chip
IntRo
CMOS technology, 0.12 µm, radiation hard ASIC, analogue
Noise Equivalent Charge
ENC = 790e +17.5e /pF
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
25ns.[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%).
6th DITANET Topical Workshop on Particle Detection
Techniques - Seville 08.11.2011
Sum
Repeater Boards
Functions:
1. Repeater for differential signals
2. Time Fast Control
IntRo
QCT
QCMA
3. Beetle Chips configuration signals
SDP
4. Carrier of voltage regulators for Beetle Chips and L0 electronics service
systems
LVA
5. ECS card: repeats the signals for the I2C configuration bus and controls
and monitors the LV regulators
LVE
Sum
6th 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
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
2. Cross – talk removal
3. Channel re-ordering
IntRo
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.
6th 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
IntRo
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
6th DITANET Topical Workshop on Particle Detection
Techniques - Seville 08.11.2011
Any questions?
Thank you
6th DITANET Topical Workshop on Particle Detection
Techniques - Seville 08.11.2011