The SVT in STARThe final device….The final device….

… and all its

connections

… and all its

connections

SDD’s: 3-d measuring devices

STAR-SVT characteristics

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 s, (TPC drift time = 50 s) anode pitch = 250 m, cathode pitch = 150 m 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 2001R. Bellwied, Snowmass 2001

Wafers: Performance

Unambiguous XY coordinates

250 m x-pitch, 20 ns y-time, ENC = 500e, vdrift = 6.5m/ns Along X (anodes) determined by anode pitch and noise.

Typically less than 10m.

Along Y (drift) determined by time bucket width, noise, and homogeneity of implanted resistors. Typically less than 20m.

R. Bellwied, Snowmass 2001R. Bellwied, Snowmass 2001

Typical SDD Resolution

R. Bellwied, Snowmass 2001R. Bellwied, Snowmass 2001

Wafers: B and T dependence

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 T-dependent. 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

R. Bellwied, Snowmass 2001 R. Bellwied, Snowmass 2001

0 1 2 3 4 5 65.2

5.3

5.4

5.5

5.6

5.7

5.8

5.9

6.0

6.1

Drif

t V

eloc

ity (m

/ns)

Magnetic Field (T)

Present status of technology

STAR 4in. NTD material, 3 kcm, 280 m thick, 6.3 by 6.3 cm area 250 m readout pitch, 61,440 pixels per detector SINTEF produced 250 good wafers (70% yield)

ALICE 6in. NTD material, 2 kcm, 280 m thick, 280 m pitch CANBERRA produced around 100 prototypes, good yield

Future 6in. NTD, 150 micron thick, any pitch between 200-400 m 10 by 10 cm wafer

R. Bellwied,Snowmass 2001R. Bellwied,Snowmass 2001

Silicon detector option for LCD

Central tracker: Silicon Drift DetectorsFive layersRadiation length / layer = 0.5 %sigma_rphi = 7 m, sigma_rz = 10 m

            Layer Radii    Half-lengths             -----------    ------------              20.00 cm      26.67 cm              46.25 cm        61.67 cm              72.50 cm        96.67 cm              98.75 cm       131.67 cm             125.00 cm       166.67 cm

56 m2 SiliconWafer size: 10 by 10 cm # of Wafers: 6000 (incl. spares)# of Channels: 4,404,480 channels (260 m pitch)

       

Silicon detector option for LCD (small detector, high field B=5T)

Forward tracker: Silicon StripFive disks uniformly spaced in zRadiation length / layer = 1.0 % Double-sided with 90 degree stereo, sigma = 7m

Inner radii      Outer radii    Z position             -----------      -----------    ----------               4.0 cm           20.50 cm       27.1 cm               7.9 cm           46.75 cm       62.1 cm              11.7 cm           73.00 cm       97.1 cm              15.6 cm           99.25 cm      132.1 cm              19.5 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

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 2001R. Bellwied, Snowmass 2001

R&D for Large Tracker Application

Improve position resolution to 5m Decrease anode pitch from 250 to 100m. Stiffen resistor chain and drift faster.

Improve radiation length Reduce wafer thickness from 300m to 150m 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.

Detectors/FEE can withstand around 100 krad (,n) PASA is BIPOLAR (intrinsically rad. hard.) SCA can be produced in rad. hard process.

R. Bellwied, Snowmass 2001R. Bellwied, Snowmass 2001

Simulation Studies

Momentum resolution Present: 20 m pos.res.,

1.5% rad.length/layer, Beampipe wall thickness: 2 mm

Future: 5 m pos.res., 0.5% rad.length/layer, Beampipe wall thickness: 0.5 mm

Two Track Resolution. Present: 500 m Future: 200 m

R. Bellwied, Snowmass 2001R. Bellwied, Snowmass 2001

Simulation Studies (cont.)

Momentum resolution Modify Position

Resolution Modify Radiation length:

Si thickness, Electronics Modify Beam Pipe Wall

Thickness

R. Bellwied, Snowmass 2001R. Bellwied, Snowmass 2001