Upgrading Leica MP PMTs to HyD or Ga/As

[Ethan Cohen]

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I am wondering if it is possible to upgrade a SP2 vintage scanhead PMT to
either HyD (APDs) or Ga/As PMTs?

I have a Hammatsu Ga/As H7421 sitting around, and wonder if it would be
difficult to integrate it into the scan head on a channel (limited of course).
The PMTs sit in a black box near the front bottom of the scan head
(according to the Leica cartoon).

Do HyD also need overcurrent protection like Ga/As heads?

Ethan Cohen, Ph.D.
CDRH/FDA labs.

[Rik van Gorsel]

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Hi Ethan,

If you have a configured and available 'X1 port' on the scan head, you
may be able to use that.
Leica has an adapter to that port that holds an exchangeable bandpass
filter that you can attach your H7421 (with Cmount) to.

Cheers,

Rik


On 4/12/2016 8:56 PM, Ethan Cohen wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> I am wondering if it is possible to upgrade a SP2 vintage scanhead PMT to
> either HyD (APDs) or Ga/As PMTs?
>
> I have a Hammatsu Ga/As H7421 sitting around, and wonder if it would be
> difficult to integrate it into the scan head on a channel (limited of course).
> The PMTs sit in a black box near the front bottom of the scan head
> (according to the Leica cartoon).
>
> Do HyD also need overcurrent protection like Ga/As heads?
>
> Ethan Cohen, Ph.D.
> CDRH/FDA labs.
>

--

Rik van Gorsel, PhD
Boston Electronics Corporation
<http://www.boselec.com/products/documents/HeimannArrays5-19-11.pdf>

[Zdenek Svindrych-2]

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Hi Ethan,
my guess is:

surely it is possible, everything is possible (not very helpful, I know).

And surely it'll be difficult (not very helpful either)...

With a lot of engineering and reverse engineering (where to get control
voltage aka gain; where to inject the signal, what amplitude and impedance
matching) you may achieve the goal, you may even use some liquid light guide
if the detector does not fit into the scanhead, but is it worth the effort?

Remember that Leica HyDs are not APDs! APDs are (typically) silicon
detectors (good response in near IR, up to 900 nm) and fast APDs (for photon
counting, aka SPADs) have very small active area (maybe 1000x smaller than a
PMT, so it may not be possible to integrate them). HyDs, on the other hand
(as far as I know), have GaAsP photocatode, so the spectral response is
similar to other GaAsP PMTs (these work  up to 700 - 750 nm only).

Overcurrent protection: even regular PMT detector modules usually have some
protection. So do GaAs and other detector modules ... unless you want to
build the power source and amplifier yourself - then it's really big project
(and not necessary cheaper, depending on how many bare detectors get fried
during the process :-).

Also, not only the electric current may damage the detector, it may be the
light itself (the noise of a PMT may increase, sometimes permanently). APDs
should not be too susceptible (no warranty).

Good luck breathing new life into an old SP2!

zdenek


---------- Původní zpráva ----------
Od: Ethan Cohen <[hidden email]>
Komu: [hidden email]
Datum: 12. 4. 2016 20:57:54
Předmět: Upgrading Leica MP PMTs to HyD or Ga/As

"*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
Post images on http://www.imgur.com and include the link in your posting.
*****

I am wondering if it is possible to upgrade a SP2 vintage scanhead PMT to
either HyD (APDs) or Ga/As PMTs?

I have a Hammatsu Ga/As H7421 sitting around, and wonder if it would be
difficult to integrate it into the scan head on a channel (limited of
course).
The PMTs sit in a black box near the front bottom of the scan head
(according to the Leica cartoon).

Do HyD also need overcurrent protection like Ga/As heads?

Ethan Cohen, Ph.D.
CDRH/FDA labs."

[Ethan Cohen]

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Rik: Thanks for the useful response.
So I should see some sort of bump on the side of the scan head if I have
this adapter?
My unit does have a C-mount.

Is this a photograph of an SP2 head or SP5 head?

Ethan.

[Jan Pala]

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Dear Ethan,

most probably your SP2 scanhead doesnt have the adaptation for X1 port.
Check this:
http://biology.illinoisstate.edu/images/confocal-schem-ISU.jpg
X1 port should be just above pinhole (7) and analyzer wheel (8), i.e.
instead of mirror there should be a modification for X1 port.

The subject of your original post was "Leica MP", i.e. it could be easy to
adapt third party detectors for RLD-NDD port of your multiphoton system.

Best regards,
Jan

On Wed, Apr 13, 2016 at 10:56 PM, Ethan Cohen <[hidden email]>
wrote:

> *****
> To join, leave or search the confocal microscopy listserv, go to:
> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> Post images on http://www.imgur.com and include the link in your posting.
> *****
>
> Rik: Thanks for the useful response.
> So I should see some sort of bump on the side of the scan head if I have
> this adapter?
> My unit does have a C-mount.
>
> Is this a photograph of an SP2 head or SP5 head?
>
> Ethan.
>

[Rik van Gorsel]

*****
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Ethan,

Photo is of SP5 scan head. Jan is right, if you do multiphoton
excitation, it would be a waste of useful photons to pass the light
through a pinhole (and all the other optical elements), and it is best
to use the RLD port.

- Rik

On 4/13/2016 5:17 PM, Jan Pala wrote:

> Dear Ethan,
>
> most probably your SP2 scanhead doesnt have the adaptation for X1 port.
> Check this:
> http://biology.illinoisstate.edu/images/confocal-schem-ISU.jpg
> X1 port should be just above pinhole (7) and analyzer wheel (8), i.e.
> instead of mirror there should be a modification for X1 port.
>
> The subject of your original post was "Leica MP", i.e. it could be easy to
> adapt third party detectors for RLD-NDD port of your multiphoton system.
>
> Best regards,
> Jan
>
> On Wed, Apr 13, 2016 at 10:56 PM, Ethan Cohen <[hidden email]>
> wrote:
>
>
> Rik: Thanks for the useful response.
> So I should see some sort of bump on the side of the scan head if I have
> this adapter?
> My unit does have a C-mount.
>
> Is this a photograph of an SP2 head or SP5 head?
>
> Ethan.
>

--

Rik van Gorsel, PhD
Boston Electronics Corporation

<http://www.boselec.com/products/documents/HeimannArrays5-19-11.pdf>

[James Pawley]

Hi all,

Don’t know anything about the layout of SP2 scan head but it is probably worth remembering a couple of points about hybrid PMTs before you start this process:

1) PMTs usually use power supplies that operate in the range of 500-1,200 volts. Hybrids commonly use 10-20kV.

2) Hybrids are particularly sensitive to being exposed to too much light when under power (every photoelectron arrives at the APD on the anode with an energy of 10-20keV and most of this energy ends up as heat.) So you would have to be very careful to interface the hybrid's power supply with the Leica control electronics in such a way that you could never expose it to too much light.

3) The good news is that, apart from having a photocathode QE that is at least as good as that of the best “normal” PMT (GaAsP?), the first stage gain of the hybrid is so high that the detector has almost no multiplicative noise. This means that its "effective QE” is between 1.5x and 2x better than most normal PMTs with the same type of photocathode.

4) GaAs photocathodes are effective in the red and near-IR because they have a low work function. The downside of this is that they tend to produce a high dark signal unless they are actively cooled. Arranging Peltier cooling (and the power needed for it) can add complexity to what is already a fairly serious project.

5) APDs have such massive multiplicative noise that they must be used in a pulse-counting mode and when used in this way, single-APD detectors are generally not fast enough to cope with the signal rates commonly found in confocals.

This problem is solved with the multi-pixel photon counter (MPPC; https://www.hamamatsu.com/eu/en/4004.html ) in which the light signal is spread out over an array of 400-1,600 APDs, all connected in parallel. But such detectors have virtually no multiplicative noise and do not require pulse counting but they have a lower fill-factor than a normal APD (reducing its effective QE) and integrating one into an existing instrument would require both cooling and the addition of the optics needed to make sure that the signal light was evenly spread over the entire active area of the device (no matter what pinhole size was used).

Good luck with your modifications. It is hard to exaggerate the importance of having the best photodetector possible.

Best,

Jim Pawley



James and Christine Pawley, 5446 Burley Place, Box 2348, Sechelt BC, Canada, V0N3A0 [hidden email]<mailto:[hidden email]>, Phone [phone], cell 1-604-989-6146



On Apr 13, 2016, at 3:49 PM, Rik van Gorsel <[hidden email]<mailto:[hidden email]>> wrote:

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Ethan,

Photo is of SP5 scan head. Jan is right, if you do multiphoton excitation, it would be a waste of useful photons to pass the light through a pinhole (and all the other optical elements), and it is best to use the RLD port.

- Rik

On 4/13/2016 5:17 PM, Jan Pala wrote:
Dear Ethan,

most probably your SP2 scanhead doesnt have the adaptation for X1 port.
Check this:
http://biology.illinoisstate.edu/images/confocal-schem-ISU.jpg
X1 port should be just above pinhole (7) and analyzer wheel (8), i.e.
instead of mirror there should be a modification for X1 port.

The subject of your original post was "Leica MP", i.e. it could be easy to
adapt third party detectors for RLD-NDD port of your multiphoton system.

Best regards,
Jan

On Wed, Apr 13, 2016 at 10:56 PM, Ethan Cohen <[hidden email]>
wrote:


Rik: Thanks for the useful response.
So I should see some sort of bump on the side of the scan head if I have
this adapter?
My unit does have a C-mount.

Is this a photograph of an SP2 head or SP5 head?

Ethan.


--

Rik van Gorsel, PhD
Boston Electronics Corporation

<http://www.boselec.com/products/documents/HeimannArrays5-19-11.pdf>