1. PACS IBDR 27/28 Feb 2002 PACS Cryo Harness1 U.Grözinger, D.Lemke, R.Hofferbert Max-Planck-Institut für Astronomie Heidelberg Based on input data from CSL, CEA, IMEC, KT, MPE

2. PACS IBDR 27/28 Feb 2002 PACS Cryo Harness2 Cryo Harness Design Criteria according to IID-A   Minimize number of wires  Minimize heat conduction  Minimize dissipation on harness

3. PACS IBDR 27/28 Feb 2002 PACS Cryo Harness3 Cryo Harness Design Criteria Instrument requirements Provide signal integrity for  14 useful bits of science data for 800 Ge:Ga-detectors and 2560 Bolometer pixels Provide stable and low noise supplies for detector bias, readout circuits, high resolution position sensors to obtain expected performance Independent supply groups for detectors to minimize risk Low resistance actuator drive lines for accurate controlling

4. PACS IBDR 27/28 Feb 2002 PACS Cryo Harness4 Cryo Harness block diagram

5. PACS IBDR 27/28 Feb 2002 PACS Cryo Harness5 Cryo Harness Uncertainties  Nonconformity IID-A vs outcome of harness study and actual knowledge e.g. Harness length => harness resistance, cable capacity… Shield coverage => EMC aspects, power dissipation  Definition of cable types by harness manufacturer (based on instrument requirements)  Till now no reliable information about availability and characteristics of requested cable types (Triax, tw. pairs…)  Use of different cable types along cryo harness (different numbers of wires/shields in Cu-cables) may cause Grounding/EMC-Problems

6. PACS IBDR 27/28 Feb 2002 PACS Cryo Harness6 Cryo Harness cable types I, acc. Cryo Harness Spec. Number of wires Cable type times used 1 Triax-cable, SST, AWG 3850 2 SST, AWG 38, shielded20 3 SST, AWG 38, shielded 12 4 SST, AWG 38, shielded 17 6 SST, AWG 38, shielded 8 8 SST, AWG 38, shielded 10 10 SST, AWG 38, shielded17 18 SST, AWG 38, shielded13 22 SST, AWG 38, shielded 4

7. PACS IBDR 27/28 Feb 2002 PACS Cryo Harness7 Cryo Harness cable types II, acc. Cryo Harness Spec. Number of wires Cable type times used 4 2 x 2 tw pairs, SST, AWG 38, shielded 16 32 16 x 2 tw pairs, SST, AWG 38, shielded 14 36 18 x 2 tw pairs, SST, AWG 38, shielded 6 2 1 x 2 tw pair, Brass, AWG 30, shielded 2 4 2 x 2 tw pairs, Brass, AWG 30, shielded 18 6 3 x 2 tw pairs, Brass, AWG 30, shielded 2 12 6 x 2 tw pairs, Brass, AWG 30, shielded 2

8. PACS IBDR 27/28 Feb 2002 PACS Cryo Harness8 Cryo Harness open items / problem areas  Due to the anticipated increase of harness length, instruments are forced to allow higher resistances and capacities => contradiction to instrument requirements  Power dissipation on Harness (e.g. actuator drive lines)  Detailed consideration of EMC aspects  Shielding efficiency (e.g. optical coverage, resistance)  Large number of different cable types

9. PACS IBDR 27/28 Feb 2002 PACS Cryo Harness9 Cryo Harness Conclusion  Issue 1 of Cryo Harness Specification completed  Harness matters are crucial for instrument performance  Confirmation about availability of requested cable types needed  Harness routing should consider EMI/EMC aspects  Harness working group established