SYSTEME D'ALIMENTATION POUR ACCELERATEUR DE PARTICULES, ET APPAREIL DE RADIOTHERAPIE EMPLOYANT CE SYSTEME

FEED SYSTEM FOR A PARTICLE ACCELERATOR AND A RADIO-THERAPY APPARATUS USING THIS SYSTEM

Abrégé anglais

A FEED SYSTEM FOR A PARTICLE ACCELERATOR
AND A RADIO-THERAPY APPARATUS USING THIS SYSTEM
Abstract of the Disclosure
A system for supplying pulsed high voltage and hyper-
frequency energy by means of a single pulse generator G
to a particle accelerator A situated at a great distance
from the generator G, the deformation of the pulses applied
to said accelerator being negligible. This system comprises
a pulse generator G, a step up voltage transformer T1
situated in the vicinity of the accelerator A, the primary
of the transformer T1 being connected to the generator G
by means of a coaxial cable L of predetermined length,
a variable resistor R enabling the shape of the pulses applied
to the accelerator to be corrected. Another transformer
T2 can supply the pulsed high voltage to the hyperfrequency
generator K delivering the HF energy to the accelerator
sections of the accelerator A.

Revendications

The embodiments of the invention in which an exclusive
property or privilege is claimed, are defined as follows:
1. A feed system for feeding a particle accelerator,
said system comprising a low impedance pulse generator situated
at a distance from said accelerator, a step up voltage transformer
having a primary winding and a secondary winding for supplying a
pulse high voltage to said accelerator and means for injecting a
high frequency energy into said accelerator, said transformer,
situated in the vicinity of said accelerator, having said secon-
dary winding connected to said accelerator by means of a short
connection and said primary winding connected to the pulse gene-
rator by means of a transmission line of predetermined length,
adjustable matching means being provided upstream of said trans-
mission line for suitably matching said pulse generator and
obtaining suitable pulses at the output end of said first trans-
former.
2. A feed system as claimed in claim 1, wherein said
pulse generator is associated with a second step up voltage trans-
former which enables a pulsed high voltage to be supplied to a
high frequency generator for delivering the high frequency energy
to said accelerator.
3. A feed system as claimed in claim 1, wherein said
adjustable matching means comprise a variable resistor.

Description

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The modulator used for supplying pulsed high voltage
to the hyperfrequency generator (for example Klystron or magnetron)
delivering high frequency energy to the accelerator cavities of a
charged particle accelerator, generally supplies the accelerator
itself with pulsed high voltage, an additional winding or a branch
being provided for this purpose in the secondary of the ~IT trans-
former situated downstream of the modulator.
But, particle sources (for example electron guns) repre-
sents high-impedance charges which, in some cases, are of necessity
situated fairly far from the high tension winding of the transfor-
mer, as is the case for example with certain radio-therapy appa-
ratus.
The high frequency generator is normally situated in
the vicinity of the modulator and the step-up voltage transformer,
whereas the accelerator, situated at a distance of several metres
from this HT transformer, receives the pulsed high voltage through
a transmission line of considerable length which is situated bet-
ween the secondary of the HT transformer and the accelerator,
generally being associated with a resistance of low value connec-
ted in parallel and having a high power consumption compared withthe power consumption of the HF generator. In addition, the
capacitance carried back by the transmission line to the level of
the primary winding of the HT transformer is of high value.
The system for feeding an accelerator according to the
invention enables these disadvantages to be obviated.
According to the invention, there is provided a feed
system for feeding a particle accelerator, said system comprising
a low impedance pulse generator situated at a distance from said
accelerator, a step up voltage transformer having a primary winding
and a secondary winding for supplying a pulse high voltage to said
accelerator and means for injecting a high frequency energy lnto
said accelerator, said transformer, situated in the vicinity of

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said accelerator, having said secondary winding connected to said
accelerator by means of a short connection and said primary wind-
ing connected to the pulse generator by means of a transmission
line of predetermined length, adjustable matching means being
provided upstream of said transmission line for suitably matching
said pulse generator and obtaining suitable pulses at the output
end of said first transformer.
For the better understanding of the invention and to
show how the same may be carried into effect, reference will be
made to the drawing accompanying the ensuing description.
The single figure shows a feed system according to the
invention for an accelerator A, this system comprising a pulse
generator G and a first step up voltage transformer Tl situated in
the vicinity of the accelerator A. The primary winding of the
transformer Tl is connected to the pulse generator G by a conven-
tional coaxial cable L having an impedance of 50 or 75 ohms for
example and a predetermined length (for example approximately 10
metres) and the secondary winding is connected to the electron
gun CA of the accelerator A. An adjustable matching system Sa is
arranged between the pulse generator G and the input end of the
coaxial cable L. This adjustable matching system Sa may be a
variable resistor connected in serie$ and having adjustable values
between 50 and 100 ohms for example. The resistance value is
adjusted for suitably loading the pulse generator G and obtaining
undistorted pulses at the output end of the transformer Tl, this
adjustable matching systèm Sa being able to correct the pulse
distorsions introduced by the coaxial line L and the windings of
the transformer Tl. The HF energy injected into the accelerator
A is supplied by a hyperfrequency generator K which may be suppli~
with high voltage by another step up voltage transformer T2 f
which the primary winding is connected to the pulse generator G
whilst its secondary high tension winding is connected to the
_ 3 _
~,j .

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hyperfrequency ~enerator K, the pulsed high voltage being applied
to the gun CK of the generator K (for example a klystron). A
hyperfrequency connecting line g enables the HF energy supplied
by the klystron K to be injected into the accelerator sections
of the accelerator A.
The feed system according to the invention may be used
with advantage in medical radio-therapy apparatus comprising a
particle accelerator A situated in the vicinity of the irradiation
head, i.e. at a fairly considerable distance from the pulse gene-
rator. I