Transcript Silicon Drift Detectors - RHIG

The SVT in STAR
The final device….
… and all its
connections
SDD’s: 3-d measuring devices
STAR-SVT characteristics
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216 wafers (bi-directional drift) = 432 hybrids
3 barrels, r = 5, 10, 15 cm, 103,680 channels, 13,271,040 pixels
6 by 6 cm active area = max. 3 cm drift, 3 mm (inactive) guard area
max. HV = 1500 V, max. drift time = 5 ms, (TPC drift time = 50 ms)
anode pitch = 250 mm, cathode pitch = 150 mm
SVT cost: $7M for 0.7m2 of silicon
Radiation length: 1.4% per layer
 0.3% silicon, 0.5% FEE (Front End Electronics),
 0.6% cooling and support. Beryllium support structure.
 FEE placed beside wafers. Water cooling.
R. Bellwied, Snowmass 2001
Wafers: Performance
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Unambiguous XY coordinates
250 mm x-pitch, 20 ns y-time, ENC = 500e, vdrift = 6.5mm/ns
 Along X (anodes) determined by anode pitch and noise.
Typically less than 10mm.
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Along Y (drift) determined by time bucket width, noise,
and homogeneity of implanted resistors. Typically less
than 20mm.
R. Bellwied, Snowmass 2001
Typical SDD Resolution
R. Bellwied, Snowmass 2001
Wafers: B and T dependence
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Used at B=6T. B fields
parallel to drift increase the
resistance and slow the drift
velocity.
The detectors work well up
to 50oC but are also very Tdependent. T-variations of
0.10C cause a 10% drift
velocity variation
Detectors are operated at
room temperature in STAR.
We monitor these effect via
MOS charge injectors
6.1
6.0
5.9
Drift Velocity ( mm/ns)
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5.8
5.7
5.6
5.5
5.4
5.3
5.2
0
1
2
3
4
5
6
Magnetic Field (T)
R. Bellwied, Snowmass 2001
Present status of technology
STAR
 4in. NTD material, 3 kWcm, 280 mm thick, 6.3 by 6.3 cm area
 250 mm readout pitch, 61,440 pixels per detector
 SINTEF produced 250 good wafers (70% yield)
ALICE
 6in. NTD material, 2 kWcm, 280 mm thick, 280 mm pitch
 CANBERRA produced around 100 prototypes, good yield
Future
 6in. NTD, 150 micron thick, any pitch between 200-400 mm
 10 by 10 cm wafer
R. Bellwied,Snowmass 2001
Silicon detector option for LCD
Silicon detector option for LCD
(small detector, high field B=5T)
Central tracker: Silicon Drift Detectors
Five layers
Radiation length / layer = 0.5 %
sigma_rphi = 7 mm, sigma_rz = 10 mm
Layer Radii
----------20.00 cm
46.25 cm
72.50 cm
98.75 cm
125.00 cm
Half-lengths
-----------26.67 cm
61.67 cm
96.67 cm
131.67 cm
166.67 cm
56 m2 Silicon
Wafer size: 10 by 10 cm
# of Wafers: 6000 (incl. spares)
# of Channels: 4,404,480 channels
(260 mm pitch)
Forward tracker: Silicon Strip
Five disks uniformly spaced in z
Radiation length / layer = 1.0 %
Double-sided with 90 degree stereo, sigma = 7mm
Inner radii
----------4.0 cm
7.9 cm
11.7 cm
15.6 cm
19.5 cm
Outer radii Z position
----------- ---------20.50 cm
27.1 cm
46.75 cm
62.1 cm
73.00 cm
97.1 cm
99.25 cm
132.1 cm
125.50 cm
167.1 cm
Vertex detector:CCD
5 layers uniformly spaced (r = 1.2 cm to 6.0 cm)
Half-length of layer 1 = 2.5 cm
Half-length of layers 2-5 = 12.5 cm
sigma_rphi = sigma_rz = 5 microns
Radiation length / layer = 0.1 %
Silicon Drift Detector Features
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Mature technology.
<10 micron resolution achievable with $’s
and R&D. Easy along one axis (anodes).
<0.5% radiation length/layer achievable if
FEE moved to edges.
Low number of channels translates to low
cost silicon detectors with good resolution.
Detector could be operated with air cooling
at room temperature
R. Bellwied, Snowmass 2001
R&D for Large Tracker Application
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Improve position resolution to 5mm
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Improve radiation length
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Decrease anode pitch from 250 to 100mm.
Stiffen resistor chain and drift faster.
Reduce wafer thickness from 300mm to 150mm
Move FEE to edges or change from hybrid to SVX
Air cooling vs. water cooling
Use 6in instead of 4in Silicon wafers to reduce #channels.
More extensive radiation damage studies.
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Detectors/FEE can withstand around 100 krad (g,n)
PASA is BIPOLAR (intrinsically rad. hard.)
SCA can be produced in rad. hard process.
R. Bellwied, Snowmass 2001
Simulation Studies
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Momentum resolution
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Present: 20 mm pos.res.,
1.5% rad.length/layer,
Beampipe wall thickness:
2 mm
Future: 5 mm pos.res.,
0.5% rad.length/layer,
Beampipe wall thickness:
0.5 mm
Two Track Resolution.
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Present: 500 mm
Future: 200 mm
R. Bellwied, Snowmass 2001
Simulation Studies (cont.)
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Momentum resolution
 Modify Position
Resolution
 Modify Radiation length:
Si thickness, Electronics
 Modify Beam Pipe Wall
Thickness
R. Bellwied, Snowmass 2001