1. Markus, Mathieu, Enrique, Rudiger, Serge
Extension of CRYO_START & CRYO_MAINTAIN logic for 120A dipole orbit corrector circuits
Markus, Mathieu, Enrique, Rudiger, Serge

2. Summary of the issue Approval closed
During commissioning of sector 45, a request for additional conditions in existing CRYO_MAINTAIN & CRYO_START logic for powering of local 120A current leads of the 120A orbit corrector circuits has been expressed by Amalia
Thermalisation points of those leads need to be surveilled during powering (as for the 60A converters) -> no powering yet of these circuits in sector 45
Some 160 circuits exist in 14 powering subsectors:
Approval closed

3. The conditions
The 120A orbit corrector circuits are using 120A conduction cooled current leads DFLES, similar to the 60A circuits
The conditions to be included in addition for powering are thus identical to the conditions already agreed for the 60A Power Permit
Beam screen temperature in corresponding cells <30K (to assure 2nd thermalization, performed at the out/inlet of the beam screen loop) – 25K for CRYO_START
All CV94x of corresponding cells are opened
Note:
The operational range of 50K<T<75K of the thermal screen will be surveilled by two alarms, triggering an on-call intervention of a cryogenic operator
Other than the 60A converters (where an independent CRYO_MAINTAIN is sent via the timing system), the 120A circuits are interlocked via the PIC

4. Proposal #1 (As in ECR)– inclusion in existing logic
120A PP
120A PP
Advantage: No change of interlock systems, change only in logic of unique CRYO_MAINTAIN signal / powering subsector
Disadvantage: Operational beam screen loop for powering of ANY circuit in the subsector (masking possible but is against Cryo policy and inhibits tuning, etc..)

5. Proposal #2 – Independent 2nd signal
120A PP
Cryo Maintain
120A
120A PP
Cryo Start
120A
Advantage: Flexibility during HWC, tuning of beam screen during initial powering
Disadvantage: Temporary solution, considerable changes of interlock PVSS and PLC logic, re-commissioning before changing to final ‘operational’ logic

6. Proposal #3 Advantage: Disadvantage: 120A PP Connection
done after e.g. PCC
120A PP
Advantage:
Keeping Flexibility for HWC without additional constraints if beam screen not yet operational at start of HWC in a sector
beam screen loop can be commissioned and tuned in parallel to other activities (no masking)
additional logic already prepared in advance by ACR, small ‘online’ intervention without PLC stop or re-load to include additional conditions once beam screen operational and before start of 120A commissioning
If MPP agrees, test plan could be followed without this condition until PCC (10A), then barrier for CRYO tests
Disadvantage:
Short re-test of cryo logic and additional inputs after modification (30 min), change of test plan for 120A circuits

7. Conclusion
After discussions with the experts (CO, Cryo, AT/CRG, …) solution #3 seems to be providing the desired functionality and flexibility for early HWC with negligible impact on the existing implementations
Logic for next sectors is being prepared now by AT/CRG and we need to decide TODAY:
Does MPP endorse the implementation of proposal # 3?
When to activate the 120A CRYO logic - Can e.g. interlock tests (0A) and PCC (10A) be done without the logic in place?
Can the 120A logic be implemented as agreed for the 60A already (much easier for AT/CRG)?
ECR will be updated and released accordingly 7