CA1290470C

CA1290470C - Dual energy food irradiator

Info

Publication number: CA1290470C
Application number: CA000562013A
Authority: CA
Inventors: Jean-Pierre Labrie; Court B. Lawrence; Joseph Mckeown; James Ungrin
Original assignee: Canada, AS REPRESENTED BY MINISTE NADA Ltd
Current assignee: Canada, AS REPRESENTED BY MINISTE NADA Ltd; IOTRON INDUSTRIES CANADA Inc
Priority date: 1988-03-21
Filing date: 1988-03-21
Publication date: 1991-10-08
Anticipated expiration: 2008-10-08

Abstract

TITLE
DUAL ENERGY FOOD IRRADIATOR

INVENTORS
JEAN-PIERRE LABRIE
COURT B. LAWRENCE
JOSEPH McKEOWN
JAMES UNGRIN

ABSTRACT OF THE DISCLOSURE

This invention describes a method which permits the generation of electron beams at two or more energy levels by a single accelerator structure powered from a single source while still retaining optimum performance from the injector.

Description

)470 Elec-tron accelerators have been used exten-sively to produce radiation to sterilize and modify materials. Linear accelerators are used where higher energy and hence higher penetration are required~ In many radiation applications, a range of energies is required and this is achieved by varying the ~F power to the structure which in turn changes the electric field gradient. A consequence of this method is that the electrons are no longer travelling at the correct velocity to be properly captured by the injector resulting in poor energy resolution and transmission of the beam.
For the irradiation of food, two specific electron energies are required viz. S MeV (for photon production) and 10 MeV. This application for a patent describes a lS method and an apparatus which permits these two energies to emerge from a single accelerator structure powered from a single source while still retaining optimum per-formance from the injector.
Brief Description of the Drawinq Figure 1 is a schematic illustration of the main components of the irradiator according to one em-bodiment of the invention.
Detailed Description of Preferred Embodiments Figure 1 shows the main components of the dual mode food irradiator. Power from the single klystron i5 split by a 4-port hybrid into two waveguide arms 2 and 4. The standing-wave accelerator structure comprises 129V4~0 an injector/accelerator section A bolted to an accelera-tor section B and uses a common cooling arrangement to maintain the same resonant Erequency in the two sections.
It is designed that radiofrequency power cannot flow between section A and section s by terminating each section in a closed full cell. Any reflected power from the sections is directed to port 3 of the hybrid.
When 10 MeV electron energy is required, power flows to both sections A and B. The electrons are cap-tured by the injector, bunched and accelerated to near the speed of light by section A and further accelerated in section B to 10 MeV. When electrons at 5 MeV are required, a shorting plate is introduced into the wave-guide driving section B reflecting all of this power into port 3 of the hybrid while leaving the fields in section A unchanged. Now the bunched and well contained beam emerging at point X can drift through the unpowered section s to emerge at point Z without loss.
In electron mode, the 10 MeV beam enters an electromaynet 10 which is achromatic and deflects the beam vertically downwards by bending all particles through 270. At the exit of the magnet, a scanning coil 12 provides a modulating magnetic field which deflects the beam within the scan horn across the exit window where it emerges to lnteract with the product.

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In photon mode, the 270 magnet is not ener-gized, hence the beam passes straight through and is diffused before impinging on a photo converter. Another scanning coil 14 is provided on the electron magnet 10 for scanning the photon converter by an electron beam. The photons generated, interact directly with the product which is presented in pallet form to take advantage of the greater penetration of the photon beam.

Claims

1. A method of generating an electron beam at more than one energy level by an electron linear accelerator, comprising steps of:
- generating RF energy for electron accelera-tion, - dividing the said RF energy into two or more parts, - applying the said divided parts of the said RF energy to separate sections of the said electron linear accelerator; and - switching on and off one or more of the said divided parts of the RF energy to adjust the energy of the electron beam.

2. An apparatus for generating an electron beam at more than one energy level by an electron linear accelerator, comprising:
- RF generating means for generating RF energy for electron acceleration, - multiport hybrid means for dividing the said RF energy into two or more parts, - the said electron linear accelerator having more than one section connected in tandem, - applying means for applying the said divided parts of the said RF energy to the said more than one section separately, and - switching means for switching on and off one or more of the said divided parts of the RF energy to adjust the energy of the said electron beam.