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39.1 GENERAL DESCRIPTION . . . . . . . . . . . . . . 39-1

39.2 APPLICATION . . . . . . . . . . . . . . . . . . 39-1

39.3 SOLID STATE SWITCHES . . . . . . . . . . . . . . 39-1

39.4 CAMAC CONTROL . . . . . . . . . . . . . . . . . 39-2

39.5 MANUAL CONTROL . . . . . . . . . . . . . . . . . 39-3

39.6 OPEN CIRCUIT DETECTION . . . . . . . . . . . . . 39-3

39.6.1 Cable and external circuits . . . . . . . . . 39-3

39.6.2 PIN diodes . . . . . . . . . . . . . . . . . . 39-3

39.7 CONSTRUCTON . . . . . . . . . . . . . . . . . . 39-3

39.7.1 Single Width CAMAC Module . . . . . . . . . . 39-3

39.7.2 Front Panel with following items: . . . . . . 39-3

39.8 DRAWING PACKAGE NUMBER . . . . . . . . . . . . . 39-4

39.9 RESPONSIBLE ENGINEERS . . . . . . . . . . . . . 39-4 CHAPTER 39 BEAM POSITION MONITOR MULTIPLEXER (R10T)

39.1 GENERAL DESCRIPTION The Relay 10-Throw single-pole module (R10T) is designed to multiplex up to ten Beam Position Monitors (BPM) to a single BPM signal processor. It is a modification of the SP10T, for use in the SLC Arcs and North Damping Ring. The solid state switch is made using PIN diodes. The switch position is controlled by a CAMAC write function, or a front-panel push-button switch. All contacts can be opened with a CLEAR command, or with the push-button, and the switch position can be read back via CAMAC.

39.2 APPLICATION When used in the Arcs and Damping Ring, separate R10T modules will be used for the vertical and horizontal BPMs. A vertical BPM has its electrodes connected to a combiner which produces a signal proportional to the vertical deviation of the beam, and this is fed into one channel of a "vertical" R10T. A different signal combination is used for a horizontal BPM feeding into a "horizontal" R10T. The outputs from each pair of R10Ts are connected to an RF Head unit where further signal processing takes place before being passed on to a Track and Hold Module (THM) where the pulse amplitudes are measured.

39.3 SOLID STATE SWITCHES PIN diodes can switch short, bipolar impulses as large as +/-15 volts, with a control current of 50 to 100 milliamp only. When the diode does not conduct, it exhibits a capacitance of 0.3 pico-farad and when it conducts, it's forward impedence amounts to only a few ohms. The bias (control current) driver circuit for each channel is adjusted to give a standard insertion loss (1.38 dB +/- 0.05%) during the initial module testing. This eliminates the need for matching or selecting diodes to give identical channel through-put characteristics. Switching from one station to another takes a few microseconds. The switches are open when the control current is zero.


BEAM POSITION MONITOR MULTIPLEXER (R10T) Page 39-2

39.4 CAMAC CONTROL o Q and X are returned true for all valid functions. o DECODING An FPLA is used to decode A, F, N, C and Z lines to allow for possible future modifications. o F23 A0-15 -- CLEAR All contacts are opened. The latches holding the data do not require a CLEAR between WRITE commands since they can be overwritten. o F22 A0-15 -- WRITE The 10 write lines control the 10 inputs of the R10T as shown below. They are latched with S1 +-------+--------+----------+---------------+ | R10T | Bus | Binary | Hexadecimal | | input | line | word | value | +-------+--------+----------+---------------+ | 1 | W1 |0000000001| 1 | | 2 | W2 |0000000010| 2 | | 3 | W3 |0000000100| 4 | | 4 | W4 |0000001000| 8 | | 5 | W5 |0000010000| 10 | | 6 | W6 |0000100000| 20 | | 7 | W7 |0001000000| 40 | | 8 | W8 |0010000000| 80 | | 9 | W9 |0100000000| 100 | | 10 | W10 |1000000000| 200 | +-------+--------+----------+---------------+ o F2 A0-15 -- READ This function tests the latched command on the transistors which close or open the PIN diode switches. The format is the same as for WRITE. Note that this readback is modified if an open circuit is detected (see below).


BEAM POSITION MONITOR MULTIPLEXER (R10T) Page 39-3

39.5 MANUAL CONTROL A channel can be selected by means of the push-button. Each push will advance the channel address by one count. The selected channel is displayed on an array of LEDs. There is a "no channel" position between channel 10 and channel 1. Any CAMAC WRITE commands will over-ride any manual selection.

39.6 OPEN CIRCUIT DETECTION

39.6.1 Cable and external circuits When a channel is addressed, a transistor injects 40 mA dc which travels along the cable to the combiner where there is a resistive splitter, so that half the current goes down each BPM cable and then to ground via the BPM electrodes. If any of the cables become disconnected or open circuited the dc voltage at the channel connector on the R10T will rise and this will be detected by a "window" comparitor connected at this point. If the transistor should fail, the voltage will fall, and this will also be detected. The output from the window detector is used in two ways. For manual selection, it inhibits the channel LED, so that if a LED does not light when stepping through the channels, if may indicate an open circuit. It also zeros the channel select bit in the CAMAC READ register, so that if a channel is selected through CAMAC and a read-back shows no selection, this can indicate an open circuit.

39.6.2 PIN diodes An additional window comparitor monitors the PIN diode drive potential to detect open or short circuited diodes. The output of the comparitor can be read at bit R11 on CAMAC F2. Logical "1" is normal, "0" denotes a fault.

39.7 CONSTRUCTON

39.7.1 Single Width CAMAC Module

39.7.2 Front Panel with following items: o 10 SMA sockets for signals from BPMs. o 1 SMA connector for output to RF Head unit. o 10 LEDs indicating selected channel o 2 LEDs indicating "N" and "X"


BEAM POSITION MONITOR MULTIPLEXER (R10T) Page 39-4 o Green LED indicating current through switching diode o Push-button to select channel

39.8 DRAWING PACKAGE NUMBER 233-313

39.9 RESPONSIBLE ENGINEERS J-C. Denard, J-L. Pellegrin, and V. Smith


 
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