Abstract: A regenerator for a cryocooler includes a cell, a flow passage, a capillary and supporting elements. A cell wall encloses a cavity with sub-cavities. A connecting passage connects a first sub-cavity to a second sub-cavity. A first cell partition is disposed between the first and second sub-cavities. The flow passage is also disposed between the first and second sub-cavities. During operation of the regenerator, helium in the cavity functions as a heat-storing material, while helium that flows through the flow passage functions as a working gas. The capillary forms a pressure-equalizing opening in the cell wall and connects the helium that functions as the heat-storing material inside the cavity to the helium that functions as the working gas outside the cavity. The supporting elements are inside the first sub-cavity and separate the first cell partition from a second cell partition. The first and second cell partitions enclose the first sub-cavity.

Abstract: A regenerator of a cryo-cooler uses helium both as a working gas and as a heat storage material. The regenerator includes cells whose exterior sides form flow channels through which the working gas flows. Each cell has connected first and second cavities enclosed by a heat-conductive cell wall. The cavities contain helium that is used to store heat. Each cells is shaped as a disk. The working gas flows both through the flow channels and around the regenerator so as to exchange heat with the helium in the cavities via the heat conducting cell wall. Each cell has a pressure-equalizing opening through the cell wall whose diameter is smaller than the thickness of the cell wall. The diameter of the pressure-equalizing opening is dimensioned to permit the pressure of the helium contained in the cell to change by a maximum of 20% during any working cycle of the cryo-cooler.

Abstract: A regenerator of a cryo-cooler uses helium both as a working gas and as a heat storage material. The regenerator includes cells whose exterior sides form flow channels through which the working gas flows. Each cell has connected first and second cavities enclosed by a heat-conductive cell wall. The cavities contain helium that is used to store heat. Each cells is shaped as a disk. The working gas flows both through the flow channels and around the regenerator so as to exchange heat with the helium in the cavities via the heat conducting cell wall. Each cell has a pressure-equalizing opening through the cell wall whose diameter is smaller than the thickness of the cell wall. The diameter of the pressure-equalizing opening is dimensioned to permit the pressure of the helium contained in the cell to change by a maximum of 20% during any working cycle of the cryo-cooler.

Abstract: A compressor device that periodically supplies compressed working gas to a cooling device loses less gas by not using a rotary valve. The compressor device includes a compressor chamber, a working gas connection, a working liquid connection, a pump, a compensation container and a membrane that is airtight and liquid-tight. The membrane divides the compressor chamber into a first volume containing a working gas and a second volume containing a working liquid. The working gas connection is coupled to the first volume, and the working liquid connection is coupled to the second volume. The pump periodically pumps the working liquid through the working liquid connection and into the second volume and as a result periodically compresses the working gas in the first volume. The membrane is constructed as a balloon or a bellows that surrounds the first volume. The compensation container contains working liquid and is connected to the pump.

Abstract: A cryostat with improved accessibility for experiments includes a cooling device, a vacuum chamber and multiple cooling levels, heat shields and experimentation places. The cooling device is thermally coupled to cooling levels that have different temperatures. The experimentation places are at the temperatures of the cooling levels and are arranged side by side when viewed from above such that each experimentation place is accessible from above and from the side. Each cooling level has an associated heat shield that also encloses an experimentation place. The vacuum chamber encloses the cooling levels. The cold plate of a second cooling level is arranged above the cold plate of a first cooling level such that a portion of the first cold plate protrudes laterally from under the second cold plate. An experimentation place is disposed above the protruding portion of the first cold plate and is accessible from above and from the side.

Abstract: Pulse tube coolers and Gifford-McMahon coolers are used to cool nuclear spin tomographs and cryopumps. To supply cooled working gas, gas compressors and in particular helium compressors are used with rotational or rotary valves. The rate at which compressed helium is introduced into the cooling device and let out again lies in the range of 1 Hz. A problem of conventional screw or piston processors is that oil from the compressor mixes with the working gas and thus contaminates the cooling device. By providing a second compressor stage, a common pump device can be used to pump in both directions, which results in a two-stage compressor device. The working gas is compressed in each flow direction of the working liquid, in one flow direction in the first compressor stage and in the opposite flow direction in the second compressor stage. Thus, the efficiency of the compressor device is improved.

Abstract: A compressor device that periodically supplies compressed working gas to a cooling device loses less of the gas by not using rotary valves. The compressor device includes a compressor cylinder, a compensation container and a drive device with an hydraulic cylinder. The compressor cylinder includes a compressor element, such as a piston or membrane, that divides the compressor cylinder into first and second volumes. The first volume contains the gas that is compressed by the compressor element. The hydraulic cylinder has a piston that is coupled to the compressor element. The compensation container contains compensation fluid and is directly connected to the second volume. The compensation container is also connected to the first volume by a gas line with a non-return valve that opens in the direction of the first volume. The drive device allows the compressed gas to be provided at a frequency required for Gifford-McMahon and pulse-tube coolers.

Abstract: A regenerator of a cryo-cooler uses helium both as a working gas and as a heat storage material. The regenerator includes cells whose exterior sides form flow channels through which the working gas flows. Each cell has connected first and second cavities enclosed by a heat-conductive cell wall. The cavities contain helium that is used to store heat. Each cells is shaped as a disk. The working gas flows both through the flow channels and around the regenerator so as to exchange heat with the helium in the cavities via the heat conducting cell wall. Each cell has a pressure-equalizing opening through the cell wall whose diameter is smaller than the thickness of the cell wall. The diameter of the pressure-equalizing opening is dimensioned to permit the pressure of the helium contained in the cell to change by a maximum of 20% during any working cycle of the cryo-cooler.

Abstract: Pulse tube coolers and Gifford-McMahon coolers are used to cool nuclear spin tomographs and cryopumps. To supply cooled working gas, gas compressors and in particular helium compressors are used with rotational or rotary valves. The rate at which compressed helium is introduced into the cooling device and let out again lies in the range of 1 Hz. A problem of conventional screw or piston processors is that oil from the compressor mixes with the working gas and thus contaminates the cooling device. By providing a second compressor stage, a common pump device can be used to pump in both directions, which results in a two-stage compressor device. The working gas is compressed in each flow direction of the working liquid, in one flow direction in the first compressor stage and in the opposite flow direction in the second compressor stage. Thus, the efficiency of the compressor device is improved.

Abstract: A low temperature device has a low temperature container with an investigational opening. A material sample to that is to be examiner is mounted on a sample-holding device in the low temperature container. A sample that is fastened to the sample holding device can be cooled to the desired temperature using a cooling device, such as a pulse tube cooler, with a cold head that is inside the low temperature container. The sample holder is disposed in the low temperature container in such a way that the sample can be seen through the investigational opening. Because the investigational opening is flexible and not rigidly connected to the low temperature container, vibrations produced by the mechanical cooling device are prevented from being transferred to the investigational opening. Thus, a vibration-sensitive investigating and manipulating device can be coupled to the investigational opening without vibrations being transferred to the investigating and manipulating device.

Abstract: A compressor device that periodically supplies compressed working gas to a cooling device loses less gas by not using a rotary valve. The compressor device includes a compressor chamber, a working gas connection, a working liquid connection, a pump, a compensation container and a membrane that is airtight and liquid-tight. The membrane divides the compressor chamber into a first volume containing a working gas and a second volume containing a working liquid. The working gas connection is coupled to the first volume, and the working liquid connection is coupled to the second volume. The pump periodically pumps the working liquid through the working liquid connection and into the second volume and as a result periodically compresses the working gas in the first volume. The membrane is constructed as a balloon or a bellows that surrounds the first volume. The compensation container contains working liquid and is connected to the pump.

Abstract: A compressor device that periodically supplies compressed working gas to a cooling device loses less of the gas by not using rotary valves. The compressor device includes a compressor cylinder, a compensation container and a drive device with an hydraulic cylinder. The compressor cylinder includes a compressor element, such as a piston or membrane, that divides the compressor cylinder into first and second volumes. The first volume contains the gas that is compressed by the compressor element. The hydraulic cylinder has a piston that is coupled to the compressor element. The compensation container contains compensation fluid and is directly connected to the second volume. The compensation container is also connected to the first volume by a gas line with a non-return valve that opens in the direction of the first volume. The drive device allows the compressed gas to be provided at a frequency required for Gifford-McMahon and pulse-tube coolers.

Abstract: A simulator for simulating treatment of biological tissue comprises a real handle with three degrees of freedom of both translation and rotation, a screen for displaying a model of the treatment area and a virtual handle, a motion detection device for detecting the three-dimensional motion of the real handle, and a computer having a simulation program that displays the virtual handle on the screen in spatial relation to the biological tissue on the basis of the motion of the real handle detected by the motion detection device. The real handle simulates a laser head that emits a laser beam for treating the biological tissue. The simulation program calculates an impinging surface of the laser beam on the biological tissue based on the spatial relation and laser parameters and calculates an energy density distribution of the laser beam within the impinging surface. The removal of tissue is displayed on the screen.

Abstract: A low temperature device has a low temperature container with an investigational opening. A material sample to that is to be examiner is mounted on a sample-holding device in the low temperature container. A sample that is fastened to the sample holding device can be cooled to the desired temperature using a cooling device, such as a pulse tube cooler, with a cold head that is inside the low temperature container. The sample holder is disposed in the low temperature container in such a way that the sample can be seen through the investigational opening. Because the investigational opening is flexible and not rigidly connected to the low temperature container, vibrations produced by the mechanical cooling device are prevented from being transferred to the investigational opening. Thus, a vibration-sensitive investigating and manipulating device can be coupled to the investigational opening without vibrations being transferred to the investigating and manipulating device.

Abstract: A cryogenic detector device includes a sensor based on a low-temperature effect and measures the temperature increase produced by the introduction of energy, such as an X-ray quantum. The smaller the thermal capacity of the sensor, the greater the temperature increase resulting from the introduction of energy and the higher the energy resolution of the sensor. Because the thermal capacity is temperature dependent, the sensor is operated in the range of comparatively small thermal capacities, i.e., in a range between 50 and 400 mK. Contrary to conventional assumptions, it was found that by keeping the three-dimensional size of the individual sensors sufficiently small and by increasing the effective sensor area, acceptable measurement results were achieved even at higher operating temperatures of the sensors in a range between 2.4 and 4.2 degrees Kelvin.

Abstract: A cryogenic detector device includes a sensor based on a low-temperature effect and measures the temperature increase produced by the introduction of energy, such as an X-ray quantum. The smaller the thermal capacity of the sensor, the greater the temperature increase resulting from the introduction of energy and the higher the energy resolution of the sensor. Because the thermal capacity is temperature dependent, the sensor is operated in the range of comparatively small thermal capacities, i.e., in a range between 50 and 400 mK. Contrary to conventional assumptions, it was found that by keeping the three-dimensional size of the individual sensors sufficiently small and by increasing the effective sensor area, acceptable measurement results were achieved even at higher operating temperatures of the sensors in a range between 2.4 and 4.2 degrees Kelvin.