1. Chain of Modules using 1cm wide Cu Tape between hybrids SP- SP+ M0 M1 M2 M3 Initial test used External shunt control (subsequently reverted) Photo shows initial (inadequate) hookup wires which have been replaced by fatter ones. Power feed is choked to reject external noise, with 1nF + 10uF thereafter to provide local HF bypass. Link between modules is ~3mm wide Cu, no coils

2. H0H1H2H3H4H5H6H7 Colum n 0123456789101112131415 ENC @ 2fC 664620640689642617636678655623655708663637636677 ENC @ 1fC 656617632678633610629669645615649692651625626658 DTN @ 1.0fC 0000000000000000 DTN @ 0.75fC 0000000003000000 DTN @ 0.5fC 9110805345148432361463132374593416169 Chain of Hybrids @ 5A (2144-3) H0H1H2H3H4H5H6H7 Colum n 0123456789101112131415 ENC @ 2fC 654610636687636610639685679630640674680648614640 ENC @ 1fC 645610627675627603625669671622632669672639609634 DTN @ 1.0fC 0000000000000000 DTN @ 0.75fC 0000000000000000 DTN @ 0.5fC 005610021185134736953857350 Chain of Modules @ 9A (2182-3) – M2 using external shunt control DTN and ENC better on average, but not for every column

3. The Bigger Picture Caps here Choke on hookup wires (not to scale!) M2 now uses internal shunt control

4. H0H1H2H3H4H5H6H7 Colum n 0123456789101112131415 ENC @ 2fC 655612636687636610639686703644651708709659623661 ENC @ 1fC 646609626675627604626667691634641695 648617653 DTN @ 1.0fC 0000000000000000 DTN @ 0.75fC 0000000000000000 DTN @ 0.5fC 005551016161123251281294683550 Chain of Modules @ 9A (2186-3) – M2 using internal shunt control H0H1H2H3H4H5H6H7 Colum n 0123456789101112131415 ENC @ 2fC 655612638686637613631672693638652691686651629657 ENC @ 1fC 645606627675627604620657684629644684675639621651 DTN @ 1.0fC 0000000000000000 DTN @ 0.75fC 0000000000000000 DTN @ 0.5fC 00654221410210320801024963346 Chain of Modules @ 9A (2187-3) – M2 using internal shunt control, “column 3” shield ties added

5. Stavelet DTN @ 0.50fC 2187-11 : M0 at 0.5fC2187-11 : M1 at 0.5fC Sum(hits): simply sum the number of hits shown in each double trigger plot 0 0 6 54 2 2 14 102 5 131 slices, each slice 100 events, each column 1280 channels

6. Stavelet DTN @ 0.50fC 2187-11 : M2 at 0.5fC2187-11 : M3 at 0.5fC Sum(hits): simply sum the number of hits shown in each double trigger plot 10 3 20 80 102 49 63 346 6

7. H0H1H2H3H4H5H6H7 Colum n 0123456789101112131415 ENC @ 2fC ENC @ 1fC 647610627675630605621655682628654691678641625655 DTN @ 1.0fC 0000000000000000 DTN @ 0.75fC 0000000000000000 DTN @ 0.5fC 004580013107711163993158347 Chain of Modules @ 9A (2188-19) – M2 SP+ link with 12nH inductor H0H1H2H3H4H5H6H7 Colum n 0123456789101112131415 ENC @ 2fC ENC @ 1fC 644610626674626603619657696640652693680641625658 DTN @ 1.0fC 0000000000000000 DTN @ 0.75fC 0000000000000000 DTN @ 0.5fC 00460011113211227831004770386 Chain of Modules @ 9A (2188-19) – M2 SP- link with 12nH inductor

8. Interpretation CofM gives better DTN than CofH – No surprises External shunt regulation of M2 gave better DTN and ENC results than internal regulation – Due to inductance of wired links between boards? – Due to location of regulation at power entry? – Due to higher Vdd? Addition of “column 3” shield ties had no effect – No surprises Adding 12nH inductor to SP+ inter-hybrid link improves DTN verys slightly – Same inductor in SP- inter-hybrid link does nothing

9. Ideas: what next? Try a star point geometry – Remove the existing inter-module ties and instead bridge the current between modules using wires (or tape) soldered to the middle of the inter-hybrid copper tape links. – Should reduce HF currents on “odd” numbered hybrids (which have worse DTN). – If caps fitted at the star point, should also be better rejection of bus noise. – Does this make any sense? Reduce loop area of hookup Caps (10uF + 1nF) from each module to common HF return foil