Posted by
Steffen Dietzel on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Zeiss-or-Olympus-tp4702418p4708891.html
While we are on the GaAsPs: Is it true that they
have a half-life of only a year? I have heard
that they decay pretty fast, independant of
usage, meaning that they loose sensitivity over
time. But I didn't have a chance to ask somebody
who has acutally worked with them.
Steffen
At 09:52 10.03.2010, you wrote:
>Just to clarify, the 780 has a GaAsP (Gallium
>Arsenite Phosphate) detector, not GaAs, the
>difference in quantum efficiency can be seen
>e.g. in the Webb multiphoton review (Nature
>Biotechnology 2003, 21, 1369). The drawback is
>that GaAsP QE dropps dramatically for
>wavelength > 700 nm, but they put a normal PMTs
>as the two additional channels on the 780, to
>cover the extended range. By the way GaAsP
>detectors are PMTs as well, it is just a
>different material of the photocathode,
>afterwards the photoelectrons are multiplied in
>the same way. GaAsP detectors reach 40% quantum
>efficiency which is about twice as sensitive as
>a normal PMT. APDs have 60-70% and a
>back-thinned CCD about 90%., so still a lot of
>signal is thrown away, not to mention the losses on the way to the detector.
>
>Andreas
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Steffen Dietzel, PD Dr. rer. nat
Ludwig-Maximilians-Universität München
Walter-Brendel-Zentrum für experimentelle Medizin (WBex)