The Successful Operation of Hole-type Gaseous Detectors at Cryogenic Temperatures

We have demonstrated that hole-type gaseous detectors, GEMs and capillary plates, can operate up to 77 K. For example, a single capillary plate can operate at gains of above 10E3 in the entire temperature interval between 300 until 77 K. The same capillary plate combined with CsI photocathodes could operate perfectly well at gains (depending on gas mixtures) of 100-1000. Obtained results may open new fields of applications for capillary plates as detectors of UV light and charge particles at cryogenic temperatures: noble liquid TPCs, WIMP detectors or LXe scintillating calorimeters and cryogenic PETs.Comment: Presented at the IEEE Nuclear Science Symposium, Roma, 200

Evaluering af Bycyklen i København.

Her i august 1997 står Bycyklen i København midt i projektets tredje sæson, og Bycyklen er ved at bide sig fast som en permanent del af det københavnske trafikbillede. Der har ikke i projektets første to leveår været midler til at foretage en systematisk undersøgelse af, hvordan Bycyklerne bruges, men der findes registreringer af cyklerne i stativerne samt en del mere journalistiske beskrivelser. Det er derfor meget vigtigt for erfaringsopsamlingen omkring Bycyklen, at Transportrådet har bevilliget støtte til en evaluering af projektet i 1997. Det er Danmarks Tekniske Universitet ved Jan Grubb Laursen, der står for undersøgelsen, og der afrapporteres i slutningen af året. Jeg har dog fået lov til at se lidt på det foreløbige materiale og kan vise nogle eksempler fra undersøgelsen. Også ZEUS-Projektet (“Zero and low Emission vehicles in Urban Societies”) under EU har givet midler til evaluering af Bycyklen i de næste par år. Det følgende er altså min vurdering af Bycyklen 1995 - 97, og jeg vil indlede med en meget kort beskrivelse af bycykelsystemet. Bycyklen må kun bruges i Københavns Indre By afgrænset af Søerne, Havnen og Christianshavns Vold, et område der svarer til P-betalingszonen. Bycyklerne frigives fra et stativ mod en pant på 20 kr., som det kendes fra supermarkeder. Pengene fås tilbage, når cyklen stilles igen i et af de 120 stativer. Og hvordan er så de første 3 år af projektets levetid er gået

A High Position Resolution X-ray Detector: an Edge on Illuminated Capillary Plate Combined with a Gas Amplification Structure

We have developed and successfully tested a prototype of a new type of high position resolution hybrid X-ray detector. It contains a thin wall lead glass capillary plate converter of X-rays combined with a microgap parallel-plate avalanche chamber filled with gas at 1 atm. The operation of these converters was studied in a wide range of X-ray energies (from 6 to 60 keV) at incident angles varying from 0-90 degree. The detection efficiency, depending on the geometry, photon energy, incident angle and the mode of operation, was between 5-30 percent in a single step mode and up to 50 percent in a multi-layered combination. Depending on the capillary geometry, the position resolution achieved was between 0.050-0.250 mm in digital form and was practically independent of the photon energy or gas mixture. The usual lead glass capillary plates operated without noticeable charging up effects at counting rates of 50 Hz/mm2, and hydrogen treated capillaries up to 10E5 Hz/mm2. The developed detector may open new possibilities for medical imaging, for example in mammography, portal imaging, radiography (including security devices), crystallography and many other applications.Comment: Presented at the IEEE Nuclear Science Symposium, Roma, Octber 200

The development of gaseous detectors with solid photocathodes for low temperature

There are several applications and fundamental research areas which require the detection of VUV light at cryogenic temperatures. For these applications we have developed and successfully tested special designs of gaseous detectors with solid photocathodes able to operate at low temperatures: sealed gaseous detectors with MgF2 windows and windowless detectors. We have experimentally demonstrated, that both primary and secondary (due to the avalanche multiplication inside liquids) scintillation lights could be recorded by photosensitive gaseous detectors. The results of this work may allow one to significantly improve the operation of some noble liquid gas TPCs.Comment: Presented at the X Vienna Conference on Instumentation, Vienna, February 200