Progress with grounding and shielding

Progress with grounding and shielding SCT system test

Contents • Description of grounding scheme • Noise injection technique • Results - new option!!

Grounding Schemes @ PPF1 - HV return line shorted to shield  HV line AC coupled to shield via 10nF cap Ned’s Smithy’s 10nF

@ PPF1 for both schemes • VDD to DGND 4.7μF • VCC to AGND 4.7μF • VCC, VDD, AGND, DGND, all signal lines to shield 1μF () • HV to HV-return 10nF

On Disk Thermal Shield Support structure PPF0 Shield OR n/c DGND Disk Radial and annular Al foils OR GND Cooling pipes + blocks

Noise injection technique • Single threshold scan with 2fC injected charge • reference scan • scan under different conditions • Assume gain = 55 • plot noise difference with respect to the reference Front side master Backside end chip Backside master chip

Results noise injection into tapesbefore some modifications Red- Smithy’s Black - Ned’s

Best Scheme - New Option • ADD DC connection at PPF0 from DGND to shield to Smithy’s scheme • Noise reduced to order 300 electrons from 2500! • BUT not been repeated since. • More measurement are on going

Progress with grounding and shielding