Capacitive level measurement for LN2 in insulated Dewars

Abstract

Construction and position of the inner cylinder (1) in the Dewar, characterized in that the cylinder forms the inner contact of the electrical capacitor formed with the outer cylinder (2).

Description

Introduction:The invention aims to develop a capacitive fill level measurement which is independent of the spatial position of the cryostat. This enables precise and reliable monitoring and control of the fill level of liquid nitrogen and enables timely refilling of the Dewar reservoir before heating of the detectors and the breakdown of the vacuum with associated severe damage.Description:The fill level measurement in previous systems is carried out by measuring the temperature of the cooled units. In cryostats as large as the ATC, this method is inadequate because reservoir refilling would be too late. Another fill level detection is difficult, since cryostats are mounted in so-called 4π spectrometers such as AGATA in arbitrary positions and orientations.Technical Structure:The invention relates to the capacitive measurement of the fill level of liquid nitrogen within insulated Dewars for keeping liquid nitrogen in stock, in particular for use in 4π spectrometers such as AGATA.Function and inventive step:Level measurements in all-layer cryostat systems have not yet existed.The capacitive measurement of the fill level of LN2 within the isolated Dewar enables precise monitoring of the fill level independently of the spatial position of the cryostat.The automatic filling of the entire system (spectrometer array) can be controlled by the fill level of each individual dewar. It is thus possible to individually control the filling. This enables a reduction in consumption of LN2 in large spectrometer arrays, which takes place during the ongoing experiments over weeks, 24 hours a day and 7 days a week.Low filling levels can be compensated for by ad hoc fillings and thus severe damage can be avoided. The evaluation of such recurrent events can also be used for fault diagnosis and for improvement in operation.This invention is described by the manufacturer of Dewars (Fa. KADEL, US, Iowa) based on discussions and requirements directed at Dr. Heinz-Georg Thomas is implemented as order work. Delivery of the Dewars is made directly by the supplier.Advantages of the Invention• Independence from the spatial position of the cryostat.• Reduction of consumption of LN2.• Real-time monitoring and control of fill level.• Emergency Filling Due to Possible Problems of Individual Detector Systems• Problem Detection• Continuous Data Acquisition to the LN2 Fill Level of All Systems within an ArrayIndustrial applicabilityThe invention is applied and marketed commercially in the production of any asymmetric AGATA triple cryostat. The invention is suitable for use in comparable cryostats for other applications.SummaryThe invention relates to a capacitive fill level measurement for liquid nitrogen in insulated Dewar systems, which operates independently of the spatial position of the cryostat and thus improves the monitoring and efficiency of germanium detector arrays.IdeasATC:The AGATA Tip Cryostat is the system that allows and allows operation of exactly three highly segmented Ge detectors. The cryostat ensures the high vacuum required, the mechanical accuracy in the positioning of the detectors, the cooling to below -180° C. and the electrical readout of the overall 111 high-resolution signal outputs.Array:A detector array is a combination of many detectors which, like a football, form a (closed) spherical shell. This is achieved with a certain number of hexagon and pentagonene, which then form the front of the detectors.Dewar:The Dewar is a vacuum insulated supply vessel for liquid nitrogen similar to a thermospot. For more complex detector systems, which can also hang flat or upside down in an array, so-called all-layer dewars are used, the internal construction of which prevents the liquid nitrogen from leaking out.LN2:Abbreviation for the English term liquid nitrogen, in the Deutsche Flussige Noff. Figure 2 represents the fact that naturally occurring nitrogen is a double molecule.Getter: Getter:A getter is a chemically reactive material that serves to maintain a vacuum for as long as possible. At the surface of the getter, gas molecules enter into a direct chemical or physical connection and are thereby removed from the volume. A standard getter is, for example, zeolite, an open-pored ceramic which, cooled to liquid nitrogen temperature, is an effective getter.Rounding:English term "ground" or "ground (electrical); the ground is the reference level which takes place with respect to a measurement or a signal is generated.FET:Abbreviation for Field Effect Transistor, a semiconductor transistor with high sensitivity and low intrinsic noise with simultaneous high gain. The electronic performance of these components is particularly good.Ge Detector:A detector system made of a high purity germanium crystal. The Ge detector system is used for the measurement of ionizing radiation.Cryostat: Cryostat:Device for cooling and maintaining a high vacuum for thermal and electrical isolation of the Ge detector systems which are installed in the cryostat.Name list:1 Inner cylinder in the Dewar, one of the two contacts for fill level measurement 2, outer cylinder and container for the liquid nitrogen (LN2) 3 outer wall of the Dewar 4 contacting the inner cylinder contact and the outer cylinder contact, serves for measuring the electrical capacitance of the electrical capacitor formed by (1) and (2).The terms refer to FIG. 1 on the sheet of drawings

Claims

Construction and location of the inner cylinder (1) in the Dewarda characterized in that the cylinder forms the inner contact of the electric capacitor formed with the outer cylinder (2).Contact (4) characterised in that it enables the measurement of the capacitance formed by (1) and (2). Specifically, the contacting with the inner cylinder must be vacuum-tight in order to ensure the insulation vacuum between (2) and (3).

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