![[SLAC Controls Department]](/grp/cd/soft/images/logo_cd.gif){kind=logo}
![[SLAC Home Page]](/grp/cd/soft/images/logo_slac.gif){kind=logo}
1.1 GENERAL DESCRIPTION . . . . . . . . . . . . . . . 1-1
1.2 SPECIFICATION . . . . . . . . . . . . . . . . . . 1-1
1.3 PULSE COUNTER . . . . . . . . . . . . . . . . . . 1-1
1.4 INTEGRATED SIGNAL READOUT . . . . . . . . . . . . 1-2
1.5 BEAM ABORT SYSTEM . . . . . . . . . . . . . . . . 1-2
1.6 HV SYSTEM . . . . . . . . . . . . . . . . . . . . 1-2
1.7 SECURITY FEATURE . . . . . . . . . . . . . . . . . 1-2
1.8 DIAGNOSTIC FEATURES . . . . . . . . . . . . . . . 1-2
1.9 CAMAC COMMANDS . . . . . . . . . . . . . . . . . . 1-4
1.10 DRAWING PACKAGE NUMBER . . . . . . . . . . . . . . 1-7
1.11 RESPONSIBLE ENGINEERS . . . . . . . . . . . . . . 1-7 CHAPTER 1 BEAM LOSS MONITOR (BLM)
1.1 GENERAL DESCRIPTION The BLM (Beam Loss Monitor) is a CAMAC module designed to monitor radiation levels in the PEP-II ring tunnels. It accepts signals from the BLM sensors (Cerenkov light dectors followed by minature photomultiplier tubes), provides diagnostics via outputs via CAMAC, and feeds the Beam Abort Logic System.
1.2 SPECIFICATION o Module width: Single o Number of Channels: 10 o Input connector: Lemo 00.250 o Connector to HV box: 4 pin Lemo 1B.304 o Connector to abort system: Lemo 00.250 o Pulse counter: 24 bits, updated every second o Integrated signal: 10 us integration time; 12 bit adc updated every second o HV power: 1000v, 10 mA
1.3 PULSE COUNTER The individual pulses from the detector are amplified, discriminated, and sent a 24 bit counter. The threshold for the discriminator is adjustable by on e 12 bit DAC for the whole module. Average maximum counting frequency is limited, by the 24 bits, to 16.7 MHz. Peak counting frequency is limited, by the counter architecture, to 40 MHz
BEAM LOSS MONITOR (BLM) Page 1-2 (25 ns between pulses). Depending on the phase relations between the input pulses and the internal clock, pulses can be missed up to 37.5 ns between pulses. Above that, all pulses will be counted. Every 1 second, the data from all counters is latched and the counters zeroed.1.4 INTEGRATED SIGNAL READOUT After the signals are picked off for the counter, they are integrated on a capacitor with a 10 us integration time. This signal is amplified and sent to a 12 bit ADC. The ADC updates each channel every 1 second.
1.5 BEAM ABORT SYSTEM The integrated and amplified signal is compared to a threshold. Each channel has a separate 12 bit DAC for the threshold setting. If it is higher and that channel is enabled for HER, the HER abort signal is sent. If it is enabled for LER, the LER abort signal is sent. The data is also latched for readout by CAMAC. The abort signals themselves are not latched.
1.6 HV SYSTEM The high voltage for the BLM dectors is supplied from a separate module powered and controlled by the CAMAC module. The CAMAC module will send 24v power and a control voltage from a 12 bit DAC. The box will return a voltage proportional to the actual high voltage out. This will be sent to a 12 bit ADC for CAMAC readout.
1.7 SECURITY FEATURE All CAMAC commands that control systems that are par of the MPS (Machine Protection System) require that ta special command first to unlock the module. These are the abort threshold settings, the high voltage control DAC, and the beam abort masks. The module must be relocked by another commnd.
1.8 DIAGNOSTIC FEATURES The abort signals form a continuous loop from module to module. An abort anywhere will force the whole loop low (abort). Signal interrupts (damaged cable, unplugged connectors, faulty modules, etc) could be difficult to locate. To help with this, there is a special diagnostic mode which forces the abort output high, regardless of the state of the input. The signal can then be traced, and the interruption located. This should only be used when there is no beam.
BEAM LOSS MONITOR (BLM) Page 1-3 Similarly, it would be difficult to tell if the inhibit signal is being received properly by the modules. There is a special test command that reads OK for 50 milliseconds after an inhibit has been received. In practice, this would read continously OK during injection (inhibits sent 40-120 Hz), and not at other times.
BEAM LOSS MONITOR (BLM) Page 1-41.9 CAMAC COMMANDS o F0 An: Read channel n (0-9) threshold set point for beam abort, (R1-R12) o F0 A10: Read threshold set point for counter discriminator, (R1-R12) o F0 A11: Read DAC set point HV, (R1-R12) o F1 An: Read channel n (0-9) ADC, (R1-R12); +/-10V 2's compliment o F1 A10: Read ADC for actual HV output, (R1-R12) o F1 A11: Read channel 11 voltage; +/-5V (not used) o F1 A12: Read channel 12 voltage; +/-5V (not used) o F1 A13: Read channel 13 voltage' +/-5V (not used) o F1 A14: Read channel 14 voltage' +/-5V (not used) o F1 A15: Read channel 15 voltage' +/-5V (not used) o F2 An: Read channel n (0-9) counter, (R1-R24) o F3 A0: Read module serial number, (R1-R16) o F3 A1: Read module id, (R1-R16) o F3 A2: Read module revision, (R1-R16) o F4 A0: Read back abort mask for HER loop, (R1-R11) Table 1 R/W Description --- ------------ 0 Channel 0 enabled 1 Channel 2 enabled 2 Channel 2 enabled 3 Channel 3 enabled 4 Channel 4 enabled 5 Channel 5 enabled 6 Channel 6 enabled 7 Channel 7 enabled 8 Channel 8 enabled 9 Channel 9 enabled 10 Abort beam For bits 0-9, if 0 then abort beam when above threshold. For bit 10, if 0 abort beam regardless of input states. Otherwise, normal operation.
BEAM LOSS MONITOR (BLM) Page 1-5 o F4 A1: Read back abort mask for LER loop (R1-R11); (See Table 1) o F5 A0: Read trip state latch, (R1-R10) Table 2 Read Bit Description ------- ------------ 0 Ch 0 was above threshold 1 Ch 1 was above threshold 2 Ch 2 was above threshold 3 Ch 3 was above threshold 4 Ch 4 was above threshold 5 Ch 5 was above threshold 6 Ch 6 was above threshold 7 Ch 7 was above threshold 8 Ch 8 was above threshold 9 Ch 9 was above threshold o F6 A1: Counter update readback, (R1) data=1 update every 10 ms data=0 update every 1 sec (R1) o F6 A2: Freeze mode readback, (R1) data=1 updates are not frozen on abort data=0 updates are frozen on abort o F6 A3: Bypass state readback, (R1) data=1 abort signals bypassed on power-off; power-off will not cause an abort. data=0 abort signals stopped on power-off. Power-off will cause an abort. Set by hardware jumpers. o F6 A4: Test abort loop input for HER loop, (R1) data=1 input abort status (GOOD); o F6 A5: Test abort loop input for LER loop, (R1) data=1 input abort status (GOOD); F6 A6: Read inhibit transition on input, (R1) data=1 inhibit transition occurred within 50ms data=0 inhibit transition did not occur within 50 ms. o F8 A0: Clear trip state latch (no data). NOTE: Data is latched and remains until cleard by F8A0. Data is available whether or not the channel is enabled for HER or LER. o F16 An: Set channel n (0-9) threshold for beam abort, (W1-W12) Module must be unlocked. Q=0 if not permitted. o F16 A10: Set threshold for counter descriminator, (R1-R12) o F16 A11: Set DAC for HV, (R1-R12) Module must be unlocked. Q=0 if not permitted. o F19 A0: Set module serial number, (W1-W16) A Wait of 10 ms is requiree before any other F19 or F3 operations. Jumper must be installed. o F19 A1: Set module id, (W1-W16) A Wait of 10 ms is requiree before any other F19 or F3 operations. Jumper must be installed.
BEAM LOSS MONITOR (BLM) Page 1-6 o F19 A2: Set module revision, (W1-W16) A Wait of 10 ms is require before any other F19 or F3 operations. Jumper must be installed. o F20 A0: Set abort mask HER loop, (W1-W11) Module must be unlocked. Q=0 if not permitted. (See Table 1) o F20 A1: Set abort mask LER loop, (W1-W11) Module must be unlocked. Q=0 if not permitted. (See Table 1) o F22 A1: Set 10ms counter update, (W1) data = 1 update every 10 ms. data = 0 update every 1 sec. o F22 A2: Set non-freeze mode (R1) data = 1 updates are not frozen on abort. data = updates are frozen on abort. o F22 A3: Dummy command. Returns X=1,Q=1 o F22 A4: Abort loop diagnostic for HER loop, (W1) data = 1 set abort loop. data = 0 set not abort loop; input is ignored Pulsed for 45 seconds. Expect X=1, Q=1. Module must be unlocked. Q=0 indicates that operation was not permitted. o F22 A5: Abort loop diagnostic for LER loop, (W1) data = 1 set abort loop. data = 0 set not abort loop; input is ignored Pulsed for 45 seconds. Expect X=1, Q=1. Module must be unlocked. Q=0 indicates that operation was not permitted. o F22 A6: Dummy command. Returns X=1, Q=1 o F24 A0: Clear abort loop diagnostics - both loops o F24 A1: Clear abort loop diagnostics - both loops o F26 A0: Set abort loop diagnostic - HER loop. Abort loop output is forced high (not abort); input is ignored. Pulsed for 45 seconds. Module must be unlocked. Expect X=1,Q=1. If Q=0 then operation was not permitted. o F26 A1: Set abort loop diagnostic - LER loop. Abort loop output is forced high (not abort); input is ignored. Pulsed for 45 seconds. Module must be unlocked. Expect X=1,Q=1. If Q=0 then operation was not permitted. o F27 A0: Test abort loop input for HER loop. Q=1 means input is high (not abort). o F27 A1: Test abort loop input for LER loop. Q=1 means input is high (not abort). o F27 A2: Test abort inhibit signal. Returns Q=1 abort inhibit is active; Q=0 if abort inhibit is not running. o 29 14: Unlock module
BEAM LOSS MONITOR (BLM) Page 1-7 o F29 15: Lock module o Z*S2: Set all internal registers to zero o X: X=1 on all commands. o Q: Q=1 on all valid commands, except where indicated. o Z: Initialize module; Set all registers and status to "0". o Power on: Same as Z.1.10 DRAWING PACKAGE NUMBER xxx-xxx
1.11 RESPONSIBLE ENGINEERS Andrew J. Gioumousis