The SVT in STAR 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 0.7m 2 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 Unambiguous XY coordinates 250  m x-pitch, 20 ns y-time, ENC = 500e, v drift = 6.5  m/ns Along X (anodes) determined by anode pitch and noise. Typically less than 10  m. Along Y (drift) determined by time bucket width, noise, and homogeneity of implanted resistors. Typically less than 20  m. R. Bellwied, Snowmass 2001

Typical SDD Resolution R. 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 50 o C but are also very T- dependent. T-variations of C 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

Present status of technology STAR 4in. NTD material, 3 k  cm, 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 k  cm, 280  m thick, 280  m pitch CANBERRA produced around 100 prototypes, good yield Future 6in. NTD, 150 micron thick, any pitch between  m 10 by 10 cm wafer R. Bellwied,Snowmass 2001

Silicon detector option for LCD

Central tracker: Silicon Drift Detectors Five layers Radiation length / layer = 0.5 % sigma_rphi = 7  m, sigma_rz = 10  m Layer Radii Half-lengths cm cm cm cm cm cm cm cm cm cm 56 m 2 Silicon Wafer 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 Strip Five disks uniformly spaced in z Radiation length / layer = 1.0 % Double-sided with 90 degree stereo, sigma = 7  m Inner radii Outer radii Z position cm cm 27.1 cm 7.9 cm cm 62.1 cm 11.7 cm cm 97.1 cm 15.6 cm cm cm 19.5 cm cm 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 2001

R&D for Large Tracker Application Improve position resolution to 5  m Decrease anode pitch from 250 to 100  m. Stiffen resistor chain and drift faster. Improve radiation length Reduce wafer thickness from 300  m to 150  m 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 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 2001

Simulation Studies (cont.) Momentum resolution Modify Position Resolution Modify Radiation length: Si thickness, Electronics Modify Beam Pipe Wall Thickness R. Bellwied, Snowmass 2001