Some proposals on HV circuits realization for segmented straw detector Leonid Kudin, Elena Chernishova,PNPI, CBM meeting, Dubna, 13-18 october

Such decision was proposed in previous CBM meeting at Darmstadt Fig.1a Fig.1

The main maxims of HV circuits realization in our opinion are following: To produce HV circuits by the way of assembling separate HV units (32 or 64 channels per unit). Easy to soldering, cleaning, drying, testing and capsulation; During units installation on the detector to minimize soldering operations (to use crimping, connectors and its elements); To provide independence in the process of the detector and HV circuits assembling; To provide convenient mounting HV circuits on the detector; To understand the problems of HV components arrangement. For this purpose breadboard (BB) was done at PNPI. All units of the breadboard can be used for detector prototype tests.

Breadboard construction There are 3 different units with different electronic components (coupling capacitors and HV resistors) placed on BB: Unit A with HV components capsulated by compound for unidirectional signal lines; Unit B analogical to unit A, but without capsulation; Unit C for providing differential translation of input signals. A B C Fig.2

Sizes and arrangement A B C Fig.3 Pads for flex cable connections ? Each of units supplies 32 channels with connections to flex cables. All GNDs provides by spring plates. We propose to install spring plates in straw during the process of wiring and attach to units mechanically (This is the line of the separate assembling straw and HV part with electronics). For the moment flex cables connections is under the question (kapton, wire ..?) A 84mm B 32.5mm C 108mm Fig.3

HV coating protection Unit A- with encapsulated SMT components for 16 channels. For others 16 channels encapsulated capacitors and SMD resistors were used. HV properties of encapsulation materials: Leak current for encapsulated area (16 channels) is less than 1 nA under HV=3kV. Leak current for SMD components under urethane conformal coating for 16 channels 5-10 nA under HV 3kV and humidity 70% Fig.4

GNDs Spring plates for GNDs can be done in different modifications: For one or two layers of straw; For outer straw surface GNDs as was shown on Fig.2; The thickness of spring plates –can be done from 25 to 50 micron. Fig.5

Thank you for attention and patience. Conclusions We are hoping, that decisions proposed above will be useful for straw detector building at Dubna; The next step in our activities is the problem of HV components choice (HV capacitors, resistors, elements of protection circuits (if need); From our side we are ready to farter cooperation with straw detector and electronics groups; Our proposal is a very preliminary solution. We are ready to changed it and adapted to concrete design in the process . Thank you for attention and patience.