System and method for irradiation with improved dosage uniformity

• US 6,683,319 B1
• Filed: 07/16/2002
• Issued: 01/27/2004
• Est. Priority Date: 07/17/2001
• Status: Expired due to Fees

• Current Assignee: Mitec Incorporated
• Original Assignee: Mitec Incorporated
• Inventors: Lyons, Stan V., Koenck, Steven E.
• Primary Examiner(s): Lee, John R.
• Assistant Examiner(s): EL SHAMMAA, MARY A
• Application Number:
  US10/187,294
• Time in Patent Office: 560 Days
• Field of Search: 430/311, 250/396.R, 250/398, 250/492.1, 250/492.2, 250/492.3
• US Class Current: 250/492.3
• CPC Class Codes: G21K 5/10 with provision for relative movement of beam source and object to be irradiated

Abstract

A system and method for providing irradiation to material shapes an electron beam into a profile having a substantially rectangular intensity distribution. The profile is deflected onto the material in a pattern with substantial overlap in a first dimension and without substantial overlap in a second dimension. In an exemplary embodiment, irradiation is provided to the material from first and second opposite sides.

Claims

1. A method of providing irradiation to material from an electron beam providing source, comprising:

operating on the electron beam to construct a profile that includes successive electron beam pulses, has an intensity distribution in a first dimension that decreases with increased distance from a center point, and has an intensity distribution in a second dimension that is substantially uniform; and

deflecting the profile onto a first side of the material in a first pattern with substantial overlap in the first dimension and without substantial overlap in the second dimension.

2. The method of claim 1, further comprising:

deflecting the profile onto a second side of the material in a second pattern with substantial overlap in the first dimension and without substantial overlap in the second dimension.

3. The method of claim 1, wherein the step of operating on the electron beam to construct a profile comprises:

passing the electron beam through a magnet structure to define a stripe having a horizontal width; and

performing a vertical sweep to move the stripe a predetermined distance in the vertical direction.

4. The method of claim 3, wherein the first dimension is horizontal and the second dimension is vertical.

5. The method of claim 3, wherein the step of performing a vertical sweep comprises:

initiating an electron beam pulse to generate the electron beam; and

during the electron beam pulse, altering a current provided to a deflection magnet to move the stripe in the vertical direction.

6. The method of claim 5, wherein the current provided to the deflection magnet is altered according to an exponential function.

7. The method of claim 6, wherein the exponential function is statistically fit to a linear function.

8. A method of providing irradiation to material from first and second opposite sides with a single electron beam providing source, comprising:

spreading the electron beam into a stripe having an expanded horizontal width with a horizontal intensity distribution that decreases along the width of the stripe with increased distance from a center of the stripe;

deflecting the stripe with an upper deflection magnet in a vertical sweep to create a profile having a vertical intensity distribution profile that is substantially uniform;

deflecting the profile with the upper deflection magnet to impinge on the first side of the material in a first pattern with substantial overlap horizontally and without substantial overlap vertically; and

deflecting the profile with a lower deflection magnet to impinge on the second side of the material in a second pattern with substantial overlap horizontally and without substantial overlap vertically.

9. The method of claim 8, wherein the step of deflecting the stripe with the upper deflection magnet in a vertical sweep comprises:

initiating an electron beam pulse to generate the electron beam; and

during the electron beam pulse, altering a current provided to the upper deflection magnet to vertically move the stripe.

10. The method of claim 9, wherein the current provided to the upper deflection magnet is altered according to an exponential function.

11. The method of claim 10, wherein the exponential function is statistically fit to a linear function.

12. A method of providing irradiation to material from first and second opposite sides with a single electron beam providing source, comprising:

spreading the electron beam into a stripe having an expanded horizontal width with a horizontal intensity distribution that decreases along the width of the stripe with increased distance from a center of the stripe;

deflecting the stripe with an upper deflection magnet in a vertical sweep to create a first profile having a vertical intensity distribution that is substantially uniform;

deflecting the first profile with the upper deflection magnet to impinge on the first side of the material in a first pattern with substantial overlap horizontally and without substantial overlap vertically;

deflecting the stripe with a lower deflection magnet in a vertical sweep to create a second profile having a vertical intensity distribution that is substantially uniform; and

deflecting the second profile with the lower deflection magnet to impinge on the second side of the material in a second pattern with substantial overlap horizontally and without substantial overlap vertically.

13. The method of claim 12, wherein the steps of deflecting the stripe with the upper deflection magnet in a vertical sweep and deflecting the stripe with the lower deflection magnet in a vertical sweep each comprise:

initiating an electron beam pulse to generate the electron beam; and

during the electron beam pulse, altering a current provided to a respective deflection magnet to vertically move the stripe.

14. The method of claim 13, wherein the current provided to the respective deflection magnet is altered according to an exponential function.

15. The method of claim 14, wherein the exponential function is statistically fit to a linear function.

16. A system for providing irradiation to material from first and second opposite sides, comprising:

an accelerator for providing an accelerated electron beam;

a magnet structure for spreading the electron beam into a stripe having an expanded horizontal width with a horizontal intensity distribution that decreases along the width of the stripe with increased distance from a center of the stripe;

an upper deflection magnet operable to deflect the stripe in a vertical sweep to create a profile having a vertical intensity distribution that is substantially uniform and to direct the profile onto the first side of the material in a first pattern with substantial overlap horizontally and without substantial overlap vertically;

a lower deflection magnet operable to direct the profile onto the second side of the material in a second pattern with substantial overlap horizontally and without substantial overlap vertically.

17. The system of claim 16, further comprising:

a controller operatively connected to the upper deflection magnet to provide a changing current to the upper deflection magnet to perform the vertical sweep of the stripe.

18. The system of claim 17, wherein the controller is operable to provide an exponentially changing current to the upper deflection magnet to perform the vertical sweep of the stripe.

19. The system of claim 18, wherein the exponentially changing current is statistically fit to a linear function.

20. A system for providing irradiation to material from first and second opposite sides, comprising:

an accelerator for providing an accelerated electron beam;

a magnet structure for spreading the electron beam into a stripe having an expanded horizontal width with a horizontal intensity distribution that decreases along the width of the stripe with,increased distance from a center of the stripe;

an upper deflection magnet operable to deflect the stripe in a vertical sweep to create a first profile having a vertical intensity distribution that is substantially uniform and to direct the profile onto the first side of the material in a first pattern with substantial overlap horizontally and without substantial overlap vertically;

a lower deflection magnet operable to deflect the stripe in a vertical sweep to create a second profile having a vertical intensity distribution that is substantially uniform and to direct the second profile onto the second side of the material in a second pattern with substantial overlap horizontally and without substantial overlap vertically.

21. The system of claim 20, further comprising:

a controller operatively connected to the upper deflection magnet and the lower deflection magnet to provide a changing current to the upper deflection magnet and the lower deflection magnet to perform the vertical sweeps of the stripe.

22. The system of claim 21, wherein the controller is operable to provide an exponentially changing current to the upper deflection magnet and the lower deflection magnet to perform the vertical sweeps of the stripe.

23. The system of claim 22, wherein the exponentially changing current is statistically fit to a linear function.

24. A method of providing irradiation to material from first and second opposite sides with a single electron beam providing source, comprising:

spreading the electron beam into a first stripe having an expanded horizontal width with a horizontal intensity distribution that decreases along the width of the first stripe with increased distance from a center of the first stripe;

deflecting the first stripe with an upper deflection magnet in a vertical sweep to create a first profile having a vertical intensity distribution profile that is substantially uniform;

deflecting the first profile with the upper deflection magnet to impinge on the first side of the material in a first pattern with substantial overlap horizontally and without substantial overlap vertically;

spreading the electron beam into a second stripe having an expanded horizontal width with a horizontal intensity distribution that decreases along the width of the second stripe with increased distance from a center of the second stripe;

deflecting the second stripe with a lower deflection magnet in a vertical sweep to create a second profile having a vertical intensity distribution profile that is substantially uniform; and

deflecting the second profile with the lower deflection magnet to impinge on the second side of the material in a second pattern with substantial overlap horizontally and without substantial overlap vertically.

25. A system for providing irradiation to material from first and second opposite sides, comprising:

an accelerator for providing an accelerated electron beam;

an upper magnet structure for spreading the electron beam into a first stripe having an expanded horizontal width with a horizontal intensity distribution that decreases along the width of the first stripe with increased distance from a center of the first stripe;

an upper deflection magnet operable to deflect the first stripe in a vertical sweep to create a first profile having a vertical intensity distribution that is substantially uniform and to direct the first profile onto the first side of the material in a first pattern with substantial overlap horizontally and without substantial overlap vertically;

a lower magnet structure for spreading the electron beam into a second stripe having an expanded horizontal width with a horizontal intensity distribution that decreases along the width of the second stripe with increased distance from a center of the second stripe;

a lower deflection magnet operable to deflect the second stripe in a vertical sweep to create a second profile having a vertical intensity distribution that is substantially uniform and to direct the second profile onto the second side of the material in a second pattern with substantial overlap horizontally and without substantial overlap vertically.