Underground detectors

Figure 3 shows the spectra from measurement of a wheat stem sample with two different detectors, above ground and underground. It clearly shows the main advantage of using underground detectors for low level environmental samples. The peaks above the 1460 keV peak can be measured with very low detection limits. 

Underground detectors observing neutrinos produced by cosmic rays in the atmosphere have measured a v i/ve > 3tio much less than expected and also a deficiency of upward going compared to downward. This could be explained by oscillations leading to the disappearance of Va with Am ... 

While most applications of nonpolar liquids in detectors involve quantities of liquid not exceeding a few liters, calorimeters and underground detectors (electronic bubble chamber) require several tens of thousands of liters of ultrapure liquid. The purification and handling of such quantities represent a qualitatively different task as compared to laboratory-style preparation. 

Underground detectors observing neutrinos produced by cosmic rays in the atmosphere have measured a much less than ex-... 

The Institute has many-year experience of investigations and developments in the field of NDT. These are, mainly, developments which allowed creation of a series of eddy current flaw detectors for various applications. The Institute has traditionally studied the physico-mechanical properties of materials, their stressed-strained state, fracture mechanics and developed on this basis the procedures and instruments which measure the properties and predict the behaviour of materials. Quite important are also developments of technologies and equipment for control of thickness and adhesion of thin protective coatings on various bases, corrosion control of underground pipelines by indirect method, acoustic emission control of hydrogen and corrosion cracking in structural materials, etc. 

Rasor, J. P., Selecting a Holiday Detector , A Collection of Papers on Underground Corrosion (Ed. George B. McComb, NACE), Vol. 4, 1st edn (1960)... 

The proposed CUORE (cryogenic underground observatory for rare events) [83] experiment is a large arrays of detectors for the research of (3(3(Ov) decay. 

Once closed inside its copper frame, the array was mounted and thermally connected to the mixing chamber of the Oxford DR installed in Hall A of the underground Gran Sasso National Laboratory. The tower was mechanically decoupled from the cryostat in order to avoid vibrations induced by pumps on the detectors and preamplifiers [98],... 

The catalyst preparation area is protected by an automatic water-spray sprinkler system that is actuated by associated heat detectors. Fixed fire water monitors surround this process area. The water for these fire protection systems is supplied through 8-inch underground water mains by three (two diesel and one electric) horizontal, centrifugal, 2500... 

The detector was placed deep underground to shield against cosmic ray background reactions. 

Most supercritical fluid equipment use CO2 non toxic, non flammable, it is particularly safe. However, CO2 build-up in closed rooms could lead to people asphyxia. It is the reason why all possible CO2 emissions (exit valves, safety valves, rupture disks,...) must be collected in a "over-dimensioned" vent line ensuring a good dispersion of the gas in the outside atmosphere. Moreover, it is highly recommended to install CO2 detectors in the equipment room but also in any connex room, for action on high power fans and operators information. Anyway, it is preferable not to operate an equipment in rooms located over other rooms, especially underground cellars, where CO2 that is heavier than air may accumulate. 

Figure 1 Schematic drawing of the underground HPGe-detector and the Pb/Cu shield together with Marinelli beaker.

Figure 2 Background spectra of the underground HPGe-detector before and after the change to an aluminium endcap.

Table 1 List of background y-ray peaks for the underground HPGe-detector before (2003) and after (2005) the installation of the new endcap as well as with mercury shield (2006-...

In underground laboratories the main source of background in HPGe-detectors is usually from radioactivity inside the detector. It is possible to improve the background by careful selection of radiopure materials. 

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