Re: Zeiss or Olympus - GaAsPs

Posted by Vladimir Ghukasyan-2 on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Zeiss-or-Olympus-tp4702418p4709009.html

Dear Steffen,

We were operating our H7422-P40 (Hamamatsu) for 4 years and I didn't
notice a significant decay with it.

Regards,
Vladimir


On Wed, Mar 10, 2010 at 8:06 AM, Steffen Dietzel <[hidden email]> wrote:

> 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
>
>
> --
> ---------------------------------------------------------------------------------------------------
> Steffen Dietzel, PD Dr. rer. nat
> Ludwig-Maximilians-Universität München
> Walter-Brendel-Zentrum für experimentelle Medizin (WBex)
>