Mitsubishi Denki Kabushiki Kaisha

Hitachi Medical Corporation

Mitsubishi Denki K.k.

Kazuki Moritsu

Takahiro Matsumoto

Takashi Inaguchi

Masashi Nagao

Hideto Yoshimura

Mitsuo Horikawa

Mitsuhiro Kishida

Shuuichi Nakagawa

Shuji Ando

Shuichi Nakagawa

Hirotaka Takeshima

Akihiro Harada

Hajime Tanabe

Yasuyuki Tahara

Takao Honmei

Shigenori Kuroda

Hiroshi Tazaki

Naoji Yoshida

Mituo Horikawa

Hisasi Oota

An open-type magnet device for MRI includes a pair of upper and lower magnet assemblies, and shims are provided on opposite sides of their cooling containers and/or in holes passing through central portions of the cooling containers so as to facilitate providing a highly homogeneous static magnetic field.

Open-type magnet device for MRI

A magnetic field producing apparatus is obtained which can easily perform a connection work, while securing a connection work space of a vortex coil, and can omit a base member. A width of a groove at an inner peripheral turned portion of a vortex coil is made wide to form a space without positionally shifting a center of the respective turned portions of the vortex coil. An inner peripheral end of the vortex coil can be easily picked up, a junction work with a connection lead can be readily performed, and also a bending work can be properly achieved.

Magnetic field producing apparatus and manufacturing method

An object of the present invention is to obtain a superconductive magnet, the size of which can be reduced by shortening the radial length of a magnetic device thereof and the refrigerating performance of which can be improved. A cylinder for fastening a refrigerator has an end facing an ambience of helium gas evaporating in a helium chamber and another end which is substantially horizontally fastened to a vacuum chamber. Further, the three-stage regenerative refrigerator is inserted and fastened to the cylinder for fastening the refrigerator. A heat insulator, such as a convection prevention tube, made of a hollow Teflon tube is wound around the outer surface of each stage of the cylinder of the three-stage regenerative refrigerator. The convection prevention tube is enclosed into a gap between the cylinder for fastening the refrigerator and the three-stage regenerative refrigerator without no undesirable gap so that heat convection of the helium gas is prevented.

Superconductive magnet

A cold accumulation type refrigerating machine having a high refrigeration efficiency. Rotation output of a stepping motor is converted to a reciprocative motion of a displacement member carrying a cold accumulator and disposed within a cylinder in which first and second closed chambers are defined above and below the displacement member, respectively. A compressed gas discharged from a compressor is introduced into the second closed chamber through the cold accumulator upon opening of a suction valve and undergoes expansion within the second closed chamber, the gas being then fed back to the compressor through the cold accumulator upon opening of an discharge valve, whereupon one cycle of refrigerating operation is completed. Rotation speed of the stepping motor is varied during every one cycle of operation by means of a pulse oscillation controller such that a time taken for the displacement member to reach a top dead center position from a time point at which the discharge valve is opened is increased while the remaining period of the one cycle is correspondingly shortened.

Cold accumulation type refrigerating machine

According to the present invention there is provided a regenerative refrigerator wherein a gas discharged from a compressor is introduced through a regenerator into a closed chamber whose internal volume changes with movement of a movable member, the movable member being disposed within a cylinder through a predetermined gap between its outer peripheral surface and the inner peripheral surface of the cylinder, and is allowed to expand therein, then is discharged again through the same route. In this regenerative refrigerator, the size, d, of the said gap is set in the range of 1/1000.ltoreq.d/D.ltoreq.1/100 relative to the inside diameter, D, of the cylinders or a gas convection preventing member is disposed in the said gap, or seals which are in contact with the inner peripheral surface of the cylinder are provided on the outer peripheral surfaces of both end portions of the movable member.

Regenerative refrigerator

A superconducting magnet which is capable of improving the refrigerating and the assembling characteristics and of composing in small size. A helium vessel 2 contains a cylindrical superconducting coil for cryogenically refrigerating it by liquid helium. A second and a first heat-shields 5 and 6 and a vacuum vessel 4 are coaxially provided so as to surround the helium vessel 2. Over the helium vessel 2, a L-letter shaped duct 50 is provided to be exposed to helium gas atmosphere being evaporated in the helium vessel 2. A refrigerator-mounting cylinder 51 has an end coupled to the L-letter shaped duct 50 through the bellows 52 and is mounted on an end surface of the vacuum vessel 4 substantially in parallel to the axial direction of the superconducting coil. A three-stage cold heat accumulation refrigerator 30 is inserted into and fixed to the refrigerator-mounting cylinder 51 for reliquefying the helium gas having been drawn into the L-letter shaped duct 50 by a third heat state 43.

Superconducting magnet and method for assembling the same

In a cryostat having a vacuum container (6), a refrigerator (2) having an elongated part (2b, 2c) extending in the vacuum container and having a cooling section (36, 37), a cooled member (4, 5) cooled by the cooling section, and a thermal coupling member (21, 27) thermally coupling the cooling section (36, 37) with the cooled member (4, 5), the thermal coupling member includes a first thermal contactor (22, 28) thermally coupled to the cooling section, and a second thermal contactor (29) thermally coupled to the cooled member, the first and second contactors mating with each other. The mating surfaces of the first and second contactors are inclined, and one of the first and second contactors is mounted such that it can be moved. A resilient member presses said one of the contactors against the other contactor. The contact pressure at the mating surfaces is thereby kept substantially constant. Partitions may be provided to divide the space within the jacket into parts thereby to reduce heat infiltration by convection. A communication tube may be provided to connect the space within the jacket to a space in which evaporated cryogen gas is staying.

Cryostat

In a cryostat having a vacuum container (6), a refrigerator (2) having an elongated part (2b,2c) extending in the vacuum container and having a cooling section (36, 37), a cooled member (4, 5) cooled by the cooling section, and a thermal coupling member (21, 27) thermally coupling the cooling section (36, 37) with the cooled member (4, 5), the thermal coupling member includes a first thermal contactor (22, 28) thermally coupled to the cooling section, and a second thermal contactor (29) thermally coupled to the cooled member, the first and second contactors mating with each other. The mating surfaces of the first and second contactors are inclined, and one of the first and second contactors is mounted such that it can be moved. A resilient member presses said one of the contactors against the other contactor. The contact pressure at the mating surfaces is thereby kept substantially constant. Partitions may be provided to divide the space within the jacket into parts thereby to reduce heat infiltration by convection. A communication tube may be provided to connect the space within the jacket to a space in which evaporated cryogen gas is staying.

In a cryostat comprising a cryogen container for containing a liquid cryogen, and a refrigerator for recondensing a cryogen gas resulting from evaporating of the liquid cryogen, the pressure within the cryogen container is detected, and when the pressure falls to a negative value due to excessive cooling, a heater is turned on to raise the temperature thereby to enhance the evaporation. As an alternative, the refrigerator may be turned off or its power may be lowered. This will increase the pressure within the cryogen container. When the pressure rises to a positive value, the heater is turned off or the refrigerator is turned on or its power is raised. Through such control, the pressure can be maintained at a constant, positive value. As a result, deformation of the cryogen container due to pressure variation is avoided, and deformation of the superconducting coil wound on the cryogen container is avoided, and the magnetic field strength and the magnetic field uniformity can be maintained constant.

In a cryogenic refrigeration apparatus includes a thermal shield, a vacuum vessel and a magnetic shield which are telescopically arranged in that order toward the exterior of a cryogenic vessel which accommodates a superconducting coil, a refrigerator for cooling the thermal shield is securely supported on the thick-walled magnetic shield. Accordingly, vibration produced by the refrigerator is suppressed by the magnetic shield, whereby noise is suppressed which is produced in the vacuum vessel connected to the magnetic shield through a bellows.

Growing community of inventors

Ako, Japan

Kazuki Moritsu