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DSSD production

DSSD production. 20 March 2003 T. Tsuboyama (KEK). Production of L1 and L2 ladders. 72 DSSDs have been ordered by HPK. Minimum requirement : 2*6 + 3*12=48 50% spares However…. Charge collection efficiency. Laser-scan study by R.Abe n-side Efficiency is uniform.

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DSSD production

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  1. DSSD production 20 March 2003 T. Tsuboyama (KEK)

  2. Production of L1 and L2 ladders • 72 DSSDs have been ordered by HPK. • Minimum requirement : 2*6 + 3*12=48 • 50% spares • However…

  3. Charge collection efficiency • Laser-scan study by R.Abe • n-side • Efficiency is uniform. • p-side floating strips. • L1-3: shows large charge deficit, worse than the estimation by capacitance network. • L4: shows charge loss, however, the loss is smaller than L1-3 DSSDs. The loss is consistent with calculation.

  4. How to improve the efficiency? • Since readout strips are healthy, the bulk and implantations may be healthy. • The metal on the floating strips is doubtful. • Tsuboyama and Hazumi visited HPK and discussed with the designer (Yamamura).

  5. Yamamura’s suggestions • Wire-bonding pads on un-depleted area is suspicious. • Large capacitance between the pad and silicon bulk. • In L4 sensors, pads are made in the depletion region. • The extra capacitance could absorb the charge induced by particles. Position of the guard ring

  6. How to recover efficiency? • Move bonding pads to the depletion region. • It is geometrically impossible in the L1-3 sensor. • Pads are in the depletion region in L4 sensor. • Remove aluminum traces from floating strips. • The metal on the floating strips is not useful. • Increase coupling capacitance between floating and readout strips. • Extending metal strips and overlaping the adjacent implantations. (Hazumi) (5)

  7. 50 50 50 50 20000 20000 20000 Example of overhang (Hazumi) Aluminum Overhang 56 Wao = 112 p+ strip 6 25 20000 20000 20000 70000 20000 1750 20000 20000 28 75 3 Unit=m

  8. R&D sensors • Short strip length sensor • P-strips in L1-3 DSSD is short (25.6mm) • The sensor becomes short accordingly. • Long strip-length sensor • The sensor will not be used in SVD2.1. • Strip length is 70 mm. • R&D for future large area sensors.

  9. Test set up • VA1TA hybrids is adopted for the test. • Test sensors are in production. • Partially functional hybrids are in KEK. • Sensors are starting the production. • Detector frames are now in KEK. • Assembly work will be done in KEK(?) Electrodes for bias Hybrid (dummy) Frame (glass epoxy) A large hole for the laser scan

  10. Plan • The R&D sensor • Delivery: End of March • Assembly and evaluation takes 1-2 weeks. • The SVD2.1 sensors • No change in the bulk and implantation. • Production starts after the test sensor is shipped. • Design of the top aluminum traces can be determined later, in May. • Delivery in September.

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