ES-7109 NEGATIVE MWPC HIGH VOLTAGE POWER SUPPLY

SCOPE:
 A power supply for use with multi-wire proportional chambers
 and other application requiring high voltage at low current. Some
 specifications follow:
         
 Output Voltage:    .3 to 7.5 Kilovolt
 Output Current:    500 Micro Amperes
 Maximum Operating Temperature:  70'C
 Drift:     <.2% 25-50'C
 Load Regulation:    <.2% 0-200 Micro Ampere
 Rise Time:    40 Milliseconds
 Lead Transient Response:   Recovers to .1% in 10 Milliseconds
 Overshoot on Turn-On:   <3%
 Internal Capacity:   .004 Microfarad
 Output Series Resistance:   10K

POWER REQUIREMENTS

 +12V - 690mA
 -12V - 690mA
 -24V -  32mA
         
 DESCRIPTION:
 The power supply is packaged with two complete units in a
 2 wide NIM module. Front panel controls are provided to adjust
 the high voltage and read directly in kilovolts.
 In designing this supply, particular attention has been given
 to reducing the stored energy. It is designed with high internal
 resistance to limit the energy which can be delivered to a
 proportional chamber under spark conditions. The supply has high
 internal gain and good transient response to maintain good output
 regulation under varying loads. The output terminal is isolated from
 the power supply filter capacitor by a 1OK resistor to limit peak
 chamber current from the power supply to less  than  one  ampere.

     The combination of moderate output resistance and trip
circuitry has been found to be an adequate protection scheme for
operating MWPC's at high rates where it is not possible to protect
chambers with large series resistors without  suffering  loss  of
gain.  Tests have been made with 1/2 meter  chambers  using  20  micron
tungsten wire and smaller chambers using 7.5 micron wire.  In all
cases the chambers survived thousands of sparks  without  wire  damage
using this supply.

     This supply contains a number of features designed to meet
the operational needs of proportional chambers.

     Fast Trip:  The power supply senses fast changes in output
current and turns off its internal DC to  DC  converter.  With  a
load short circuit or spark, the stored energy will be dissapated
in a millisecond or less, most of the energy going into the internal
resistance of the power supply.  At  higher  output  voltages  the
circuit is sensitive enough to trip out from corona without any
visible sparking.

     Trip Reset:   The power supply by switch  selection  will  either
remain tripped, or reset automatically after a few 'hundred milli-
seconds.

     Slow Trip:   The power supply will trip from slowly applied
loads which exceed a current trip level which is set to 80% of the
full scale meter reading.

     Current Monitor:    A Lemo connector is provided  which  monitors
chamber current scaled IOV = 1 millampere.  A current zero front
panel trimpot and careful guarding of the  output  current  allow
measurements of chamber current to 1 nanoampere with  a  typical  DVM.

      Voltage Monitor:   A Lemo connector is provided which monitors
 chamber voltage scaled 1V = 1 kilovolt.

     Trip Monitor:    The trip monitor is a TTL compatible open
 collector output that is grounded when either supply is tripped.

 A bridged Lemo connector provides the OR of the trip signal for the
 two supplies.  This allows daisy-chaining a number of supplies to
 one alarm circuit.