400 Mev Line Beam Position Monitors

S. Lackey



There are fifty-two position monitors in the 400 MeV line that connects the Linac to the Booster.  These position signals are divided into three VMEbus, VxWorks/MOOC style front end computers which digitize the position and some selected intensities.   


The data is sampled at a 5 MHz rate for as long as the gate signal from the gate generator is present.    At the falling edge of the last gate signal, the gate generator sends a signal into the external interrupt of the VME crate.  The  interrupt service routine saves the position of the pointer to the data just taken and averages the positions and intensities over the entire time that beam is present ( determined experimentally and set in software).


The three nodes are named BPM399, BPM400 and BPM401.   BPM399 includes the positions from the horizontal and vertical detectors Q1,Q2, Lam, Q3, Q4 and Q5.   Also the intensities from Q1,Lam, Q3 and Q5.    BPM400 includes the horizontal and vertical positions from Q6, Q7, Q8, Q9, Q10, Q12, and Debuncher along with the vertical position at Q11 and the horizontal position at Q13.   BPM400 intensities are from Q8, Q11,Q13 and upstream of the septum.  BPM401 includes the vertical position from Q13 and the horizontal and vertical positions from Q15, Q16, H23, Q17, Upstream of the septum and downstream of the septurm,  at the Foil, downstream of Long 1,  Short 1, upstream of Long 1 and Short 24.   The intensities from BPM401 include downstream of the septum, upstream and downstream of L1 and Short 24.  In addition BPM401 also has four “Extra Inputs” that come from special electronics and are called Sine of Phase, Cosine of Phase, Injection Delta P sine and Injection Delta P cosine.


Data is taken on all beam pulses automatically unless disabled by turning off the data taking.   To view the data or toggle data taking on or off,  use the application page written by Bill Marsh on page B32.   The “Extra Inputs” information is displayed on B33,  also written by Bill Marsh.


Physical Location of VME crates and Spares


BPM399 is in  Relay Rack #LG1-RR4-1

BPM400 and 401 are in Relay Rack #G24-RR6-2


Spare A/Ds, SSM and Processor Board (MV2400 or MV2300) can be found in Sharon Lackey’s office.  The SSM is necessary as the external interrupt comes into the system via the general purpose input of the SSM.   The SSM also is used for remote reboot.   Boot code is found at:





The source is checked into CVS under 400mevBpm


Typical Problems:


No data being taken --             Check to make sure that there is beam,  the gate signals are present,  the clock signals are entering the cards.

                                                Make sure that data taking is toggled on (displayed on line 12 of page B32).

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