The nlcta will use EPICS for monitoring the low level RF system.
The nlcta consists of 4 RF stations, each with its own IOC. A Sun Sparc Station may isolate the network from the rest of SLAC, with SLAC on le0 and the IOC's on le1.
INSTRUMENTATION: Module Sta 0 Sta 1 Sta 2 Sta 3 ------------------- ----- ----- ----- ----- NI vxiCpu030 IOC 1 1 1 1 HP e1428a Digitizer 2 1 1 1 HP e1472a Video Mux 3 2 2 2 TEK Vx4792 AFG 2 2 2 2
The HP e1428a is a two channel digitizer with a minimum bucket width of 1ns. The instrument has an internal raw data buffer of 8k points per channel. The 1428 is a message based instrument with data memory mapped into A24 space. The 1428 takes some 120ms from the digitize command to the completion SRQ. A preliminary driver is available.
The HP e1472a is a 4x6 video signal multiplexer. The 1472 is register based, mechanical coaxial relay device. The switches have a mtbf of 1e6 operations. The maximum switch rate is 30Hz. A preliminary driver is available. The TEK Vx4792 is single channel, message based, 12-bit Arbitrary Function Generator. 64KB is mapped into A24 space, but, is not used or specified by Tektronix. Reading/writing to this A24 memory does not seem to effect the AFG. The 4792 has a minimum bucket width of 4ns. The device has shown rise times of 3.7ns. The 4792 is a message based device, requiring on the order of 2 seconds to load and process a waveform of 512 points. This was not a precise measurement. The output of the AFG must be turned off in order to load a new waveform. The 4792 has a catalog of waveforms that holds up to 200KB(?) of waveform data. It is anticipated that several waveforms will be loaded into each AFG. BEWARE: the AFG's are paired, one for I and an associated one for Q. This pairing must be maintained. There is no driver for this instrument.
Each station will have an e1428 and two e1472's dedicated to monitoring I&Q detected signals from the RF Station and associated low level components. Station 0 will monitor a minimum of 9 pairs of I&Q signals, and the other stations will monitor a minimum of 7 pairs. There may be some non-I&Q, and/or non-paired waveforms monitored. Each of the signals consists of some 500 points.
The injector, Station 0, will have an e1428 and one e1472 dedicated to a future feedback loop.
The 4792 is a single channel Arbitrary Function Generator. Each station will have two 4792 AFG's to provide modulation input to the I&Q modulator for the RF signal to the TWT, and, subsequently the klystron. I&Q modulation waveforms will be loaded into the respective AFG's. The waveforms consist of 512 points. Speed requirements may make it necessary to install 4 AFG's in each station and select the input to the I&Q modulator with Mux channels.