Uniform raster pattern generating system

• US 6,380,545 B1
• Filed: 08/30/1999
• Issued: 04/30/2002
• Est. Priority Date: 08/30/1999
• Status: Expired due to Fees

• Current Assignee: Jefferson Science Associates, Llc
• Original Assignee: Southeastern Universities Research Association, Inc.
• Inventors: Yan, Chen
• Primary Examiner(s): Anderson, Bruce C.
• Application Number:
  US09/385,803
• Time in Patent Office: 974 Days
• Field of Search: 250/396.ML, 250/396.R, 250/398, 250/492.2
• US Class Current: 250/396.0ML
• CPC Class Codes: H01J 37/147 Arrangements for directing or deflecting the discharge along a desired path H01J37/045 take precedence; lenses H01J37/10

Abstract

A conventional particle generation and magnet configuration are used in combination with a relatively low-power power amplifier, a resonant loop magnet driver system, an amplitude modulator that induces a homogeneous amplitude function proportional to (t)^½ and, when individual X and Y magnets are used, a precision phase shifter that induces a 90° phase shift in the applied power to one of the magnets to produce a circular raster pattern of virtually uniform density.

Claims

1. A uniform density raster pattern generating system comprising:

A) a particle beam generator;

B) at least one magnet directing the trajectory of a particle beam generated by said particle beam generator;

C) a magnet powering circuit comprising;

i) a low-power power amplifier driving each of said at least one magnet;

ii) a resonant mode amplifier circuit between said low-power power amplifier and said at least one magnet for stepping up power from said power amplifier to said at least one magnet; and

iii) a device selected from the group consisting of;

a) an amplitude modulator; and

b) a triangular current source biasing a diode, that induces a homogeneous amplitude function proportional to (t)^½

on the waveform of power supplied from said power amplifier; and

D) a control device that serves to maintain the balance of said magnet powering circuit.

2. The uniform density raster pattern generating system of claim 1 wherein said resonant mode amplifier circuit comprises in series with said magnet and said power amplifier;

A) an impedance converter; and

B) a capacitor bank

operating at resonant frequency.

3. The uniform density raster pattern generating system of claim 2 wherein said impedance converter comprises a toroid transformer.

4. The uniform density raster pattern generating system of claim 3 wherein said toroid transformer is a ferrite toroid transformer.

5. The uniform density raster pattern generating system of claim 4 wherein said toroid transformer is a ferrite toroid transformer having a ratio of primary winding to secondary winding of 10:

1.

6. The uniform density raster pattern generating system of claim 5 wherein said ferrite toroid transformer comprises a pair of ferrite toroid transformers each having an I.D. of 5.5 cm stacked together.

7. The uniform density raster pattern generating system of claim 2 wherein said capacitor bank comprises a series of snubber capacitors.

8. The uniform density raster pattern generating system of claim 7 wherein said impedance converter is a toroid transformer.

9. The uniform density raster pattern generating system of claim 7 wherein said snubber capacitors are polypropylene snubber capacitors.

10. The uniform density raster pattern generating system of claim 2 further including a current probe that detects the current flow in said resonant mode amplifier circuit and communicates the same to said control device.

11. The uniform density raster pattern generating system of claim 2 operating at a frequency of about 24 kHz.

12. A uniform density raster pattern generating system comprising:

A) a particle beam generator;

B) a pair of magnets individually directing the trajectory of a particle beam generated by said particle generator in the X and Y directions;

C) a magnet powering circuit comprising;

i) a device selected from the group consisting of;

a) an amplitude modulator; and

b) a triangular current source biasing a diode, that induces a homogeneous amplitude function proportional to (t)^½

on the waveform of;

ii) a main waveform generator output whose signal is split between individual low-power power supplies feeding power via individual resonant mode amplifier circuits to each of said magnets; and

iv) a precision phase shifting device in one portion of said split signal that shifts the phase of that signal 90°

; and

D) a control device connected to said amplitude modulator and said main waveform generator that controls said uniform density particle beam raster system.

13. The uniform density raster pattern generating system of claim 12 wherein each of said resonant mode amplifier circuits comprises in series with said individual magnets and said individual low-power power supplies:

A) an impedance converter; and

B) a capacitor bank

operating a resonant frequency.

14. The uniform density raster pattern generating system of claim 13 wherein said impedance converter comprises a toroid transformer.

15. The uniform density raster pattern generating system of claim 14 wherein said toroid transformer comprises a ferrite toroid transformer having a ratio of primary to secondary windings of 10:

1.

16. The uniform density raster pattern generating system of claim 15 wherein said ferrite toroid transformer comprises a pair of ferrite toroid transformers each having an I.D. of 5.5 cm stacked together.

17. The uniform density raster pattern generating system of claim 14 wherein said capacitor bank comprises a series of snubber capacitors.

18. The uniform density raster pattern generating system of claim 12 operating at a frequency of about 24 kHz.

19. A method for producing a uniform density raster pattern in a device comprising a particle beam generator and at least one magnet directing the trajectory of a particle beam generated by said particle beam generator comprising the steps of:

A) generating a homogeneous amplitude function proportional to (t)^½

;

C) feeding said homogeneous amplitude function proportional to (t)^½

to a power amplifier connected to said magnet in series via a resonant mode amplifier circuit so as to control the amplitude of the output of said power amplifier;

D) powering said magnet with said power amplifier; and

E) controlling the operation of said magnet using a control device.