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>About 2 years ago, when I was building a 16-channel spectral detector for
>our multiphoton microscope with the R5900U-xx-L16 linear PMT array as a
>detector, I was told by Hammamatsu that for photon counting, I will be
>better off using the original model with the standard bilalkali
>photocathode, rather than using the newer super- or ultralakali models,
>since the older model has much lower dark counts (and can be purchased as a
>photon counting model R5900P-00-L16, tested for low-dark counts).
>The peak QE around 400 nm was OK for our purpose, since besides fluorescent
>proteins, we are interested in second harmonics signal from collagen, which
>on our system is between 350 and 400 nm.
>
>I wonder if there is going to be a hybrid multi-anode PMT.



Hi Stan,

A hybrid multi-anode PMT is an interesting idea. But I think that the 
10-20kV voltages used on the hybrid PMT might not be easy to 
implement given the small electrode geometry found on multi-anode 
PMTs.

I am also interested in your comment on GaAsP PCs on linear array 
PMT. I would have guessed that the PCs were small enough not to have 
much signal but then I checked and the PC area of this model is 12.5 
mm2 not 1mm2 as on some of the other linear models

Pulse counting is a relatively good idea for these multi-anode 
detectors for a number of reasons.

1) the electron-multiplier part has very high multiplicative noise 
(so you gain more effective QE by eliminating it).

2) as the total light signal is split between many parallel channels, 
pulse-pileup is less of a problem.

3) their small size can result in short output pulses and therefore 
fast count rates.

However, one must always be looking at the data rates to be sure that 
pulse pileup is not a problem

Best

Jim Pawley

***************************************************************************
Prof. James B. Pawley,               		            Ph. 
608-238-3953              	           
21. N. Prospect Ave. Madison, WI 53726 USA 
[log in to unmask]
3D Microscopy of Living Cells Course, June 11-23, 2011, UBC, Vancouver Canada
Info: http://www.3dcourse.ubc.ca/	    Applications due by March 15, 2011
	       "If it ain't diffraction, it must be statistics." Anon.

>Stan Vitha
>Microscopy and Imaging Center
>Texas A&M University
>BSBW 119
>College Station, TX 77843-2257
>
>On Sat, 22 Jan 2011 16:24:44 -0600, James Pawley <[log in to unmask]> wrote:
>
>>
>>I echo Mark's cautions. There are long
>>discussions of these matters in Chapter 12 and
>>Appendix 3 of the Handbook. With respect to the
>>URL Mark sent out, ultra bialkali with a maximum
>>QE of about 43% looks very good BUT:
>>
>>1) It occurs at a wavelength of 350 nm, well into
>>the near UV where we really seldom have need for
>>a detector in confocal-type micrsocopy.
>>
>>
>>Cheers,
>>
>>Jim Pawley


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