L3 Station Voltage Configurations

A6

HV updated v19.

FE emitter M1.C3 detuned on 25.01.2023 (v24)

Reduced v20 after V[e]RG[e] study 11.08.2022

Reduced for radiation.

MAX reduced v20 after V[e]RG[e] study 11.08.2022

First measurements with MARWIN indicated ~mSv/h neut rate at A22, which was later identified to be caused by M4.C3. This cavity has now been detuned and the VS configuration modified (loss of 10 MV).

Successfully re-established 17.4 GeV operation point, based on re-identification of limits on each RF station. Max SP have been adjusted to reflect these new numbers. HIGH-V config is now set to match the new max SP values. HIGH-V config now supports 16.5 GeV user run with margin for any L3 RF station failure. 

Reduced-V has now been adjusted to give one spare station margin at 14 GeV beam operation. All stations have been set to 620 MV with the exception of A6 and A9, which are set to 100MV below their radiation-limited maximum voltage. (A19 and A23 are more than 100MV below their radiation-limited max in this configuration).

During startup after COVID-19 shutdown. MARWIN recorded 1.2 mGy/h at A6 during the high-voltage operation for BBA. On 26.05.2020 this was discovered to be due to poor M-S phase alignment which actually lead to a higher voltage operation than reported. A6 limit was subsequently checked with MARWIN and re-confirmed. The original 100 uSv/h margin left originally was removed since piezo operation now stabilises the cavity tuning. See

https://ttfinfo.desy.de/elog/XMLlist?file=/XFELelog/data/2020/22/26.05_M/2020-05-26T11:28:14-00.xml&xsl=/elogbook/xsl/elog.xsl&picture=true

Two changes to config:

A18 after V[e]RG[e] studies: A18, resulting in detuning of M3.C4 due to excessive radiation (MARWIN neutron limit).

A16 change in VS.CAL_SCA after BB-Calibration (1.0 → 1.17)

Several stations changed as a result of issues ramping up to >17 GeV for BBA (6-10.04.22)

• A6 MARWIN shows increased FE neutron peak: reduced by 35MV
• A10 indicated strong soft-quenching in M3.C8, which, although not new, caused cryo issues. Reduced by 35 MV.
• A16  reduced quench field observed in M3.C8. Reduced by 25MV.
• A20 reduced quench field observed in M1.C6. Reduced by 20MV.
• A23 strong cryo-instability (soft quenching) observed in M3.C7, later identified with MARWIN as a very strong FE. M3.C7 detuned. Note that station is still constrained by high FE (MARWIN 500 uSv/h limit). Reduced by 35MV

Configurations now include MODULATOR HV and ON-CREST operation.

• MOD HV is now reduced for REDUCED-ENERGY (originally REDUCED-VS), primarily tor reduced running costs.
  • MAX-OP-VS also reflects a lower value, now limited by the klystron. 
  • These numbers are currently conservatively set to operations VS values for those stations whose MOD HV has been reduced wrt HIGH-ENERGY configuration.
    • True limits needs to be experimentally verified.
• ON-CREST operation is now indicated. These stations are not included in the LINAC ENERGY MANAGER server. 
  • For the HIGH-ENERGY configuration, A12, A16, A21 and A23 are currently run on-crest with a VSUM reduced by 10% to reduced dark current radiation rates.

This release also includes a major format change to the page.

Note: no VS values have been changed in this release.

Updated (reduced) MAX SP for A11 and A21 following V[e]RG[e] studies:

 A21, A11 V[e]RG[e] studies 11.08.2022

Reduced A20 max VS from 815 to 795 MV (20MV) after V[e]RG[e] study (see logbook entry)

Increased A25 HV by +50V to avoid klystron saturation.

VS.CAL_SCA modified for A23, A24 (BBCAL data) 

MAX_OP_VS change:

A23: 765 MV → 842 MV (modified 12.09.22)

A24: 730 MV → 788 MV (modified 19.09.22)