PVX-4130 High-Voltage Pulse Generator

1. General Description

The DEI PVX-4130 pulser is a high-voltage solid-state pulser designed to drive capacitive loads such as acceleration grids and deflection plates. It generates an output voltage swing of 6000 volts, with an output current of 30 amperes peak and 0.1 amperes continuous, producing very flat voltage pulses to DC into a capacitive load.

The PVX-4130 can generate single-ended output pulses from ground to +6000 V or from ground to −6000 V, and can also generate pulses originating from a voltage offset from ground. This offset can be from −6000 V to +6000 V, with a maximum power-supply voltage differential (V_high − V_low) ≤ 6000 V.

2. Specifications

All specifications are measured into a 50 pF load connected with 4 feet (~1.2 m) of RG-58 (50 Ω) coaxial cable, at 6000 V output.

The PVX-4130 can drive loads of a few picofarads to several hundred picofarads, limited by its maximum power dissipation. At lower load capacitances and/or voltages below 6000 V it can operate above 10 kHz. Power dissipated when driving a capacitive load is approximated by CV²F, where C is the total load capacitance (load + cable + the 100 pF internal capacitance of the PVX-4130; RG-58 adds ~30 pF/ft), V is the pulse voltage, and F is the pulse repetition frequency. Given the maximum dissipation of 100 W, this formula approximates the maximum load capacitance, frequency, and/or voltage. Contact BNC for resistive or inductive loads.

3. Safety

The high voltage of this device dictates the use of caution when operating or servicing. The following summarizes general precautions that must be observed during all phases of operation and repair.

3.1 Operating Safety Summary

Power source. The PVX-4130 is designed to operate from a source that will not apply more than 240 VAC between the supply conductors or between either supply conductor and ground. A protective grounding connection through the AC power cord is essential.

Grounding. The PVX-4130 is grounded through the grounding conductor of the AC power cord. To avoid electric shock, plug the unit into a properly wired receptacle before making any input or output connections. Use only a power cord in good condition.

Cover removal. To avoid personal injury, do not remove the covers and do not operate the unit with the covers removed. The covers do not contain a safety interlock.

General operating precautions. Do not remove the input or output cables while the pulser is in operation. Never short-circuit the output. Any pulsed-power system can trigger randomly on transients — whenever the unit is on, or dangerous voltage is present in the chassis, assume a pulse can appear on the output connector.

3.2 Servicing Safety Summary

The PVX-4130 contains dangerous voltages and stored energy. BNC strongly recommends that all repairs and adjustments be performed by factory-qualified personnel. Do not perform internal repair or adjustments unless another person capable of rendering first aid and resuscitation is present.

4. Operating Considerations

Output cabling. The PVX-4130 drives capacitive loads with fast rise times; because output current is limited, lower capacitance gives faster rise time. The unit ships with a 4-foot Teflon-insulated RG-58 coaxial cable (30 pF/ft) and is series-terminated in the cable’s 50 Ω characteristic impedance. Use the shortest cable possible for the fastest rise times and best pulse fidelity.

Load simulation. The unit is tested with a 50 pF capacitive load connected to the output with 4 feet of RG-58 coaxial cable.

Trigger input. A trigger of +5 V ±1 V into 50 Ω with a rise time <20 ns is required to gate the PVX-4130 on. Set the trigger amplitude using a 50 Ω load (for example a 50 Ω scope input) before connecting to the trigger input. A trigger greater than +5 V into 50 Ω can cause pulse stretching.

Pulse voltages +V IN and −V IN. The pulser is rated at a maximum output of ±6000 VDC; ensure this is not exceeded. When the input gate is high, V_high is connected to the output; when the gate is low, V_low is connected. A negative-going pulse can be produced by logically inverting the input gate. V_high should always be equal to or greater than V_low, but never more than 6000 V above it. For single-ended operation, ground the unused power-supply input.

5. Controls & Indicators

6. Preparation for Use

Initial inspection. After unpacking, inspect the unit for exterior mechanical damage and inspect the power input cord and input power module for obvious signs of damage. If the unit is damaged, notify the carrier immediately.

Electrical installation. Standard units ship ready for use with a nominal 110–240 VAC input. The input power cord terminates in a three-prong polarized plug; inserting it into a compatible grounded receptacle automatically grounds the unit. Do not operate without a grounded AC input.

Power-up check. Before connecting the pulse generator, set it to deliver a +5 V (±1 V) pulse into 50 Ω at roughly 500 Hz with a 1 µs pulse width. Connect the positive supply to +V IN and the negative supply to −V IN (for +6000 V single-ended output, connect −V IN to ground; ground any unused supply input) with both supplies off. Plug in AC power and turn on the front-panel POWER switch — the POWER LED should light. Connect the pulse generator to the GATE BNC, connect the load to the rear output, and monitor the output at V MON. Slowly raise the high-voltage supplies; the unit should produce an output pulse following the incoming trigger.

7. Operating Instructions

Power-up. After completing the power-up procedure, adjust the driver for the application: monitoring the output on an oscilloscope (via the internal voltage monitor or a high-voltage probe at the load), set the output amplitude by adjusting the high-voltage power supplies. Set the output pulse width and recurrence frequency with the input pulse generator; the output follows the input trigger but does not replicate its exact duration because of asymmetric system propagation delays.

Power-down. Set the high-voltage supplies to zero, turn the high-voltage supplies off, turn off the PVX-4130 power switch, then disconnect AC power.

8. Troubleshooting

Fuses. To avoid fire hazard or damage, use only the fuse type listed on the rear panel. Fuse replacement should be performed by qualified personnel only, with the AC power cord disconnected. The power MOSFETs are board-mounted; if they need replacement, return the unit to the factory.

9. System Failure Modes

The PVX-4130 generates large-amplitude current pulses with very fast rise and fall times, and has limited over-current or over-voltage protection. It is the user’s responsibility to ensure the interconnect cables and load do not create transients, over-current, or over-voltage conditions that could damage the unit — failure to do so voids the warranty.

Over-current failure. When the output is shorted, the PVX-4130 can deliver in excess of 30 A (depending on cabling and supply settings), which exceeds its specifications. The unit offers limited protection against shorts and arcs to ground, but operating into a short for an extended period may damage the unit, load, and/or cabling.

10. Warranty & Service

Berkeley Nucleonics (DEI) warrants equipment it manufactures to be free from defects in materials and workmanship under conditions of normal use for one year from the date of shipment to the original purchaser. OEM, modified, and custom items are warranted for ninety (90) days from date of shipment. BNC will repair or replace, at its option, any product shown to be defective within the warranty period. Equipment claimed to be defective must be returned, transportation prepaid, with a preauthorized return authorization. This warranty does not apply to any product that has been repaired or altered by unauthorized persons, subjected to misuse or neglect, or used other than in accordance with furnished instructions.

Factory service. Berkeley Nucleonics Corporation, 2955 Kerner Blvd., San Rafael, CA 94901. Phone: (415) 453-9955. Email: info@berkeleynucleonics.com. Web: www.berkeleynucleonics.com. Document version 9100-0218 Rev 4.