Synchrotron radiation source and method of making the same

Abstract: A synchrotron radiation source and a method of making the same are concerned. An assembly of a beam absorber (1) for synchrotron radiation beams and a piping (2) for cooling the beam absorber (1) is mounted in a charged particle beam duct (5) of a bending section (10) for bending a charged particle beam. Fixed to at least one of straight ducts (8) connectable to the opposite ends of the charged particle beam duct (5) is a piping guide duct (7) through which the beam absorber cooling piping (2) is drawn to the outside, so that the assembly of the beam absorber (1) and beam absorber cooling piping (2) can readily be mounted in the synchrotron radiation source.

Description: This invention relates to a synchrotron radiation (SR) source and a method of making the same, and more particularly relates to an SR source of the type having a beam absorber for SR beams provided in a charged particle beam duct of a charged particle beam bending section and a method of making the same. The orbit of a charged particle beam is deflected inside the charged particle beam duct of the bending section to cause the charged particle beam to radiate an SR beam and the interior of the charged particle beam duct must be maintained at vacuum to minimize the loss of the charged particles due to its collision with other different particles. However, when the SR beam directly irradiates the wall of the charged particle beam duct, the irradiated portion, conventionally made of stainless steel or aluminum alloy, undergoes a photo-excited reaction to discharge a large amount of gas and as a result the interior of the charged particle beam duct can not be maintained at high vacuum. The amount of discharged gas is very large, measuring 10 times to 100 times the amount of gas outgoing merely owing to thermal desorption, and it has been envisioned to suppress the gas discharge by providing a beam absorber at a portion, where the SR is irradiated, of the interior wall of the charged particle beam duct. More specifically, the beam absorber is made of a material which has a low photo-excited gas discharge coefficient so that the amount of gas discharged from the surface and interior of the material by a photo-excited reaction concomitant with SR irradiation can be small, and the beam absorber is used to suppress the generation of gas. Conventionally, as discussed in IEEE, Transactions on Nuclear Science Vol. NS-32, NO. 5, October 1985, pp. 3354-3358, a beam absorber having a linear or approximately linear form is mounted in a charged particle beam duct by being inserted thereinto through an insertion port dedicated to the beam absorber and which is formed in the outer circumstantial wall of the charged particle beam duct. The mount structure for beam absorber described in the above literature is well adapted for relatively large-scale SR sources in which the radius of curvature of the charged particle beam duct of charged particle beam bending section is larger and there is sufficient room. The prior art pertains therefore to technology of large-scale SR sources and fails to take small-scale SR sourses into account. Should the conventional mount structure for the linear or approximately linear beam absorber be applied to small-scale SR sources in which the radius of curvature of a bending section is small, in other words, the curvature of a charged particle beam duct of the bending section is large the linear beam absorber could not cover or profile the overall circumference of the bending section of large curvature, with the result that there remain portions on the interior wall of the charged particle beam duct which are irradiated directly with the SR. To solve this disadvantage, a number of insertion ports dedicated to beam absorbers have to be provided over the overall circumference of the bending section but actually, because of necessity to provide the bending section with SR beam lines for guiding SR beams, there is almost no room for the provision of dedicated insertion ports over the overall circumference of the bending section. Accordingly, the conventional mount structure for the linear beam absorber is totally unsuited for application to small-scale SR sources. The EP-A3-0265797, which is considered as state of the art according to Article 54(3), discloses a synchrotron comprising an acceleration line with straight and curved path sections. Magnets are associated to the curved path sections for generating a magnetic field which deflects the orbit of the charged particle beam inside that curved path sections. In each curved path section an absorber is mounted having holes formed therein through which a coolant may flow. The object of the invention is to provide a small-scale SR source which can permit easy mount of a beam absorber, and to provide a method of making the above SR source. This object will be solved by the features of claim 1 and 9, respectively. Dependent claims are directed on preferred embodiments of the invention. By drawing the beam absorber cooling piping through the piping guide duct fixed to the straight duct, the beam absorber can be mounted easily in the charged particle beam duct even in the case of small-scale SR sources. Preferred embodiments of the present invention will now be described in conjunction with the accompanying drawings, in which: Fig. 1 is a plan view illustrating a first embodiment of SR source according to the invention; Fig. 2 is a sectional view taken on the line II-II of Fig. 1; Fig. 3 is a perspective view illustrating a beam absorber and a beam absorber cooling piping used in the Fig. 1 SR source; Fig. 4 is a sectional view taken on the line IV-IV of Fig. 3; Fig. 5 is a schematic diagram showing the overall construction of a small-scale SR source incorporating the invention; Fig. 6 is a plan view illustrating a second embodiment of SR source according to the invention; Fig. 7 is a plan view illustrating a third embodiment of SR source according to the invention; and Figs. 8, 9 and 10 are plan views showing the step sequence of mounting the beam absorber in accordance with the invention. Referring now to Figs. 1 and 2, a first embodiment of SR source according to the invention will be described. As shown in Figs. 1 and 2, the SR source has a semi-circular, approximating a C shape, bending section 10 for bending a charged particle beam B. Referring particularly to Fig. 1, the charged particle beam B travelling on an orbit 6 of charged particle beam at a straight duct 8 enters an opening of one end of a charged particle beam duct 5, passes through the charged particle beam duct 5 and leaves the other end thereof. The charged particle beam duct 5 of the bending section 10 is encompassed with a bending electromagnet 9, as particularly shown in Fig. 2, and the orbit of the charged particle beam is deflected by the flux of a magnetic field generated by the bending electromagnet 9 to cause the charged particle beam tracing the deflected orbit to radiate an SR beam 4 which is taken out of the source through an SR guide duct 3. Mounted in the charged particle beam duct 5 are a beam absorber 1 and a piping 2 for cooling the beam absorber. The beam absorber 1 is adapted to suppress the generation of gas under irradiation of SR beams. The beam absorber cooling piping 2 is drawn to the outside through a piping guide duct 7 which is fixed to a straight duct 8 by making a predetermined angle to the charged particle beam orbit 6 so as to jut obliquely outwardly and the piping 2 is connected at its tip to a heat exchanger not shown. Since the interior of the charged particle beam duct 5 must be maintained at vacuum, the beam absorber cooling piping 2 is airtightly fixed to the end of the piping guide duct 7 by welding. The charged particle beam duct 5 has a channel G through which the beam absorber 1 and beam absorber cooling piping 2 are guided. The beam absorber 1 and beam absorber cooling piping 2 received in the channel G are immune to mechanical shock or vibration. Separate beam absorber 1 and beam absorber cooling piping 2 may be put together by brazing or welding or alternatively a unitary assembly of beam absorber 1 and beam absorber cooling piping 2 may originally be prepared. The overall construction of the beam absorber 1 and beam absorber cooling piping 2 used in the bending section 10 of the Fig. 1 SR source is illustrated in Fig. 3. SR beam guide ports or windows 11 are formed in the beam absorber 1 shown in Fig. 3. The beam absorber 1 is preferably made of a material of low photo-excited gas discharge coefficient which can discharge a small amount of gas under irradiation of light or photons, preferably, less than 10⁻⁶ molecules/photon for the purpose of the present invention. As the low photo-excited gas discharge coefficient material, a single crystalline material having a high purity of 99.99% or more, for example, high-purity copper or aluminum may be used. Typically, the beam absorber 1 and beam absorber cooling piping 2 shown in Fig. 3 are formed as a unitary assembly which has a sectional form as shown in Fig. 4. With the construction of the present embodiment described previously, since the beam absorber cooling piping 2 can be drawn through the piping guide duct 7 fixed to the straight duct 8 regardless of the magnitude of the radius of curvature of charged particle beam duct 5 included in the bending section, there results an excellent effect that the beam absorber 1 can readily be mounted in the charged particle beam duct 5 even in the case of small-scale SR sources. Fig. 5 is a schematic showing the overall construction of a small-scale SR course incorporating the present invention. Referring to Fig. 5, a charged particle 13 injected into an electronic input system 14 moves along the charged particle beam orbit 6 set up in the charged particle beam duct 5. The movement of the charged particle along the orbit 6 of charged particle beam is controlled by means of control system 12, acceleration control system 16 and orbit adjustment magnet 15 and as described previously, the charged particle radiates an SR beam while passing through the bending section 10. Other embodiments of the invention are illustrated in Figs. 6 and 7. Referring particularly to Fig. 6, there is illustrated a second embodiment of SR source wherein piping guide ducts 7 are provided to straight ducts 8 connectable to the opposite ends of the charged particle beam duct 5. As in the first embodiment, each piping guide duct 7 makes a predetermined angle to the charged particle beam orbit 6 to jut obliquely outwardly. Advantageously, in accordance with this embodiment, halves of an assembly of beam absorber 1 and cooling piping 2 therefor can be inserted independently into the opposite ends of the charged particle beam duct to complete the same assembly as that of the first embodiment directed to the insertion into one end of the charged particle beam duct. In a third embodiment, piping guide ducts 7 are provided to straight ducts 8 connectable to the opposite ends of the charged particle beam duct 5, as in the case of the Fig. 6 embodiment, but each piping guide duct 7 makes a predetermined angle to the charged particle beam orbit 6 to jut obliquely inwardly so as to meet the existing positional relationship to the source to peripheral equipments. Obviously, the Fig. 7 embodiment may be modified such that a piping guide duct 7 is provided for only one end of the charged particle beam duct 5. A method of making the SR source described previously, more specifically, a method of mounting the assembly of the beam absorber 1 and beam absorber cooling piping 2 in the charged particle beam duct 5 will be described with reference to Figs. 8, 9 and 10. (1) Firstly, as shown in Fig. 8, the opposite end portions of the arcuate beam absorber 1 are respectively inserted into the opposite end openings of the charged particle beam duct 5. (2) Subsequently, as shown in Fig. 9, the beam absorber 1 is moved circumferentially of the charged particle beam duct and located at a predetermined position in the charged particle beam duct. (3) Finally, as shown in Fig. 10, the opposite end portions of beam absorber cooling piping 2 going beyond the opposite ends of the charged particle beam duct 5 are bent outwardly in directions of arrows C and D, respectively, with the bent portions drawn through the piping guide ducts 7 fixed to straight ducts 8, and the straight ducts 8 are connected to the charged particle beam duct 5. In order to maintain airtightness of the charged particle beam duct, the connection of straight ducts 8 to charged particle beam duct 5 and fixing of beam absorber cooling piping 2 to piping guide duct 7 are effected by airtight welding. Vacuum pumps required for evacuating the charged particle beam duct 5 may be placed inside the bending section 10 or may be connected to the straight ducts 8.

Claims: A synchrotron radiation source comprising a bending section (10) for bending a charged particle beam (B) having a substantially sectoral or semi-circular charged particle beam duct (5) mounted with a beam absorber (1) and a piping (2) for cooling the beam absorber, a bending electromagnet (9), encompassing said charged particle beam duct, for generating a magnetic field which deflects the orbit (6) of the charged particle beam inside said charged particle beam duct, and straight ducts (8) connected to both ends of said charged particle beam duct (5), characterized in that at least one of said straight ducts (8) is provided with a piping guide duct (7) through which said beam absorber cooling piping (2) is drawn to the outside. A synchrotron radiation source according to claim 1, characterized in that each straight duct (8) is provided with a piping guide duct (7). A synchrotron radiation source according to claim 1, characterized in that said piping guide duct (7) makes a predetermined angle to said charged particle beam orbit (6) to jut obliquely outwardly with respect to the synchrotron radiation source. A synchrotron radiation source according to claim 1, characterized in that said piping guide duct (7) makes a predetermined angle to said charged particle beam orbit to jut obliquely inwardly with respect to the synchrotron radiation source. A synchrotron radiation source according to claim 1, characterized in that said charged particle beam duct (5) has a channel (G) through which said beam absorber (1) and beam absorber cooling piping (2) are guided. A synchrotron radiation source according to claim 2, characterized in that each of said piping guide ducts (7) makes a predetermined angle to said charged particle beam orbit (6) to jut obliquely outwardly. A synchrotron radiation source according to claim 2, characterized in that each of said piping guide ducts (7) makes a predetermined angle to said charged particle beam orbit (6) to jut obliquely inwardly. A synchrotron radiation source according to claim 2, characterized in that said charged particle beam (5) duct has a channel (G) through which said beam absorber (1) and beam absorber cooling piping (2) are guided. A method of making a synchrotron radiation source as claimed in claim 1, characterized in that said method comprises the steps of: in order to mount said beam absorber (1) and beam absorber cooling piping (2) in said charged particle beam duct (5), inserting the opposite end portions of said beam absorber (1), which has precedently been made to be arcuate, and the opposite end portions of said beam absorber cooling piping (2) in openings of the opposite ends of said charged particle beam duct (5); moving said beam absorber (1) and beam absorber cooling piping (2) along said charged particle beam duct and locating them at a predetermined position in said charged particle beam duct; bending the opposite end portions of said beam absorber cooling piping going beyond the opposite ends of said charged particle beam duct; drawing the bent end portions of said beam absorber cooling piping through piping guide ducts (7) fixed to said straight ducts (8) so that said bent end portions are mounted in said straight ducts; and connecting said straight ducts to said charged particle beam duct.

Inventors: IKEGUCHI TAKASHI, KUROISHI KAZUO, MATSUMOTO MANABU, SONOBE TADASHI, UEDA SHINJIRO, IKEGUCHI, TAKASHI, KUROISHI, KAZUO, MATSUMOTO, MANABU, SONOBE, TADASHI, UEDA, SHINJIRO
Applicants: HITACHI LTD, HITACHI SERVICE ENG, HITACHI SERVICE ENGINEERING CO., LTD., HITACHI, LTD.
Application year: 1988
Main classification: H05H7
IPC codes: H05H13, H05H7, G21K5