Bunch Arrival-time Monitors

BAM System Functionality

The Bunch Arrival-time Monitor (BAM) uses a relative measurement method which compares the timing of each electron bunch against a laser pulse provided by the optical reference system (LbSync); to the same time reference, the pump-probe lasers are phase-locked.

The unit of the BAM data are picoseconds. The x-axis is given in microseconds, showing the bunch filling pattern as defined in the main timing system.

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BAM Locations at XFEL

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Machine operation SASE 1 SASE 2 SASE 3
47.I1

414.B2

1932M.TL

1932S.TL

414.B2

1932M.TL

1932S.TL

414.B2

1932M.TL

1932S.TL
181.B1
203.B1
392.B2
414.B2
1932M.TL
1932S.TL

Description of Data Sources

The original DOOCS property of the BAM data has an array length of 7222 entries, and is filled in a 9 MHz pattern

The length of 7222 is derived from an underlying 9 MHz bunch pattern with 800 μs macro-pulse at FLASH: (800 * 1.3 / 144) * 1000 = 7222 entries. While for XFEL this number should be ( 600 * 1.3 / 144 ) * 1000 = 5416 entries. However, a special decision was made to keep 7222 entries during the process of server development in agreement with the software experts at MSK and MCS since they have to deliver a data structure that accommodates the needs of different user groups.

Mapping the recorded BAM to different SASEs

TODO:

Properties

Spectra

LOW_CHARGE_ARRIVAL_TIME

Calibrated arrival time data from the “low-charge channel”: - calibrated arrival time for all bunches and all sub-macropulses - full length = 7222 entries in 9 MHz pattern - x-axis: picoseconds

Integer Values

For converting to binary word with 12 bits to display status bits/logic plot.

BAM_STATUS.1

Submacropulse 1 (RF Flattop 1) general status of the BAM Channel
  • bit 0 = data is valid,
  • bit 1 = at least 1 bunch is requested/allowed from main timing,,
  • bit 2 = calibration is on,
  • bit 3 = internal feedback is on,
  • bit 4 = tuning mode is on

BAM_STATUS.2

Submacropulse 2 (RF Flattop 2) general status of the BAM Channel
  • bit 0 = data is valid,
  • bit 1 = at least 1 bunch is requested/allowed from main timing,,
  • bit 2 = calibration is on,
  • bit 3 = internal feedback is on,
  • bit 4 = tuning mode is on

BAM_STATUS.3

Submacropulse 3 (RF Flattop 3) general status of the BAM Channel
  • bit 0 = data is valid,
  • bit 1 = at least 1 bunch is requested/allowed from main timing,
  • bit 2 = calibration is on,
  • bit 3 = internal feedback is on,
  • bit 4 = tuning mode is on

BAM_ERROR

General error code of the BAM System:
  • bit 0 = no error
  • bit 1 = error from front-end,
  • bit 2 = link not locked,
  • bit 3 = MLO not locked,
  • bit 4 = error from Motor.1 (for Submacropulse 1),
  • bit 5 = error from Motor.2 (for Submacropulse 2),
  • bit 6 = error from Motor.3 (for Submacropulse 3),
  • bit 7 = error from Motor T (for time-delay between “low-charge channel” and “high-charge channel”),
  • bit 8 = toroid connection time-out,
  • bit 9 = link connection time-out,
  • bit 10 = MLO connection time-out

Detailed documentation:

https://confluence.desy.de/display/SDiagPublic/BAM+Data+Structure