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High Voltage Systems Section

Power Converters Developed by HVSS

Systems for ARPF

1. Scanning Magnet Supply
   
   
2. Microcontroller based fully programmable bipolar reference generator
   
   
3. Interlock Unit
   
   
4. Collimator Magnet Precision Power Supply
   
   
5. Scanning Interlock system
   
   
6. Pulsed Selector Magnet Power Supply
   
   
7. -50 kV /1A HV Electron Gun Pulse Power Supply
   
   

Scanning Magnet Supply

Four numbers of fully programmable Scanning Magnet Supplies have been developed for 10 MeV Linacs for+ ARPF with a peak current rating of 10 A. The current controlled supply can feed a seven segmented programmed current into the scanning magnet ( 44mH, 0.24 Ohms) load. While the rise time is programmable from 50 ms to 1000 ms , the fall time is fixed at 5 ms. This will yield better dose uniformity on the irradiated product. The scheme uses an IGBT based full bridge. Bipolar PWM switching is used to achieve the required profile of the current through the scanning magnet. A microcontroller C8051F040 based reference generator allows the user to set the current reference in local mode.


Microcontroller based fully programmable bipolar reference generator

A C8051F040 based fully programmable bipolar reference generator has been developed. The reference values can be entered and programmed through a 4 x 4 keypad with values being displayed over a 20 X 4 alphanumeric LCD display. Six numbers of reference can be programmed and stored. The reference can be programmed in seven segments with each segment having a different ramp rate. The programmed reference is generated through two inbuilt 12 bit DACs. The generator also generates a synchronizing trigger pulse to disable the beam current by shutting off the RF power during ramp down period of 5 ms. The software for controller has been developed in C language using Keil X51 compiler.

Interlock Unit

Five numbers of interlock units have been developed. The interlock unit senses the currents of magnet power supplies and generates a trip signal for RF system in case of under or over current of any of these power supplies output current. The noise filters have been incorporated in the unit to avoid spurious tripping.



Collimator Magnet Precision Power Supply

These supplies are rated for 10 V / 2 A with a setting resolution of 1 mA. The stability of the supplies is better than ± 100 ppm. It uses a series regulator scheme to achieve the required performance.





Bipolar Steering Magnet Precision Power Supply

These power supplies are CC and rated for 10 V / 2 A, with a setting resolution of 10 mA. The stability of the supplies is better than ± 500 ppm. It uses a series regulator scheme to achieve the required performance. The power has polarity reversal feature by switching the output using a relay. These supplies can be operated from remote and they have all protection features as O/C,O/V, Over Temp and short circuit etc. Total 25 nos of these power supplies have been developed and tested.



Scanning Interlock system

The system senses the current of the beam line magnet supplies of the LINAC including focusing, collimator, centring and scanning coil supplies. It generates a trip signal in case of under or over current in any of the mentioned supplies to put off the RF power and hence the beam.



Pulsed Selector Magnet Power Supply

It was required to study the beam profile of a single pulse of electron beam generated in the 10 MeV LINAC being developed for ARPF. The pulse selector supply feeds a continuous current of 15 A through the pulse selector magnet to bend the electron beam into a beam dump. Once in every 10 seconds, it sets the current to zero in less than 2.5 ms for a duration of 1 ms to enable the selection of a single beam pulse for its current profile study. A two switch forward converter topology is used and inductive load is made to resonate with input DC link capacitor to boost the DC input voltage to achieve the required current ramp down and ramp up time of less than 2.5 ms with a low input voltage of 100V.



-50 kV /1A HV Electron Gun Pulse Power Supply

An electron gun is being developed with different design parameters for electron Linacs. A -50 kV high voltage pulse supply was developed for beam extraction from the gun. A step up high voltage transformer was switched using an IGBT to get the required high voltage pulse of -50 kV across the gun. A RCD clamp was used in the primary circuit to shape the voltage pulse output. The high voltage transformer was made using resin casting to achieve the required insulation. One ampere of beam current was extracted using the supply.