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21.1 GENERAL DESCRIPTION . . . . . . . . . . . . . . 21-1
21.2 MODE OF OPERATION. . . . . . . . . . . . . . . . 21-2
21.2.1 RF Drive Amplitude and Phase. . . . . . . . . 21-2 CHAPTER 21 MODULATOR KLYSTRON SUPPORT UNIT (MKSU)
21.1 GENERAL DESCRIPTION The MKSU, together with the Phase-and-Amplitude Detector (PAD) and the RF Driver Unit (the I-Phi-A), provides all the control and monitoring facilities for running a high-power klystron. The MKSU and the PAD are both controlled by a Parallel-Input-Output- Processor (POIP), which provides the connection to the local microcluster and the VAX. The services provided by the MKSU can be summarised as follows: o Control and monitoring of the amplitude and phase of the RF drive to the klystron. o Control and monitoring of the SLED cavity tuner position. o Control and monitoring of the current supply to the klystron electromagnet. o Control and monitoring of the trigger pulse for the modulator o Aquisition of status and fault information from the klystron and modulator. o Aquisition of slowly varying analog parameters, such as electromagnet current, klystron cooling-water temperature rise, klystron cathode power etc. o Aquisition of samples of rapidly varying signals, such as klystron beam voltage and current, input and output RF power, etc. The time of sampling is a variable, so that fast time-plots (FTP) can be built up. o Provision of hard and software interlocks for the modulator trigger.
MODULATOR KLYSTRON SUPPORT UNIT (MKSU) Page 21-2 The types of signals involved for the different services are shown in the following matrix: + Analog Signal |+ Video Signal ||+ Digital Signal ||| ||| + Voltage Digitized ||| |+ Waveform Digitized (FTP) ||| ||+ Peak Value Digitized ||| ||| ||| ||| + Analog Control ||| ||| |+ Digital Control ||| ||| || + Hard Interlock Chain ||| ||| || |+ Software Permissive ||| ||| || || *.. *.. *. .. Klystron Drive Request (I-Phi-A) .*. .** .. .. Klystron Drive Monitor (I-Phi-A) ..* ... .* .. Klystron Phase Control (I-Phi-A) ..* ... .* *. SLED Status **. **. .. .. SLED RF Phase (PAD) **. **. .. .. SLED RF Amplitude (PAD) *.* *.. *. *. Focus Magnet .*. .** .. .. Klystron RF Forward Power (FE) .*. .** .. .* Klystron RF Reflected Power (RE) ..* ... .. *. Klystron Water .*. .** .. .* Pulse Beam Volts .*. .** .. .* Pulse Beam Current ..* ... .* .. Modulator Status and Control *.* *.. .. *. Waveguide Vacuum *.* *.. .. .* Klystron Vacuum *.. *.. .. .* Klystron Water Temperature *.. *.. .. .. Klystron Heater Power *.. *.. .. .. MKSU Power Supplies *.. *.. .. .. PAD Power Supplies
21.2 MODE OF OPERATION.
21.2.1 RF Drive Amplitude and Phase. The RF drive for the klystron comes through the I-Phi-A unit from the sector drive line, which is driven by a small klystron (the sub-booster). The drive level is controlled by a high-power, solid-state, S-band attenuator installed in the I-Phi-A chassis. Current is provided from the MKSU, and is controlled by a 12-bit DAC. Up to 200 mA is provided in steps of 50 uA. The highest current results in the lowest attenuation and thus highest drive. The MKSU can monitor the current being sent to the attenuator. The drive phase is controlled by a rotary S-band "Fox" type high-power phase shifter. This is driven by a stepping motor, giving 2880 steps per revolution of the drum. Each revolution introduces 720 degrees of
MODULATOR KLYSTRON SUPPORT UNIT (MKSU) Page 21-3 phase shift at S-band. (1/4 degree per step). The Fox phase shifter is equipped with a pin and an opto-detector to allow the software to "home" the mechanical drum and establish the integrity of the drive mechanism.