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Applied Detector Corporation
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General Information

1. A simple receiving inspection test

We are now starting to ship more detectors to our new and old customers. Here we describe a simple inspection test to determine whether the detector is damaged during shipping.

Starting now, ADC will add a black Delrin cap (US $50.00), power supply PS-2 (US $475.00) LEMO power cable (3 feet or 1 meter) with connectors on both ends (US $175.00). Upon receiving our detector, our customer only needs an AC power source (either 110 V, 220 V), liquid nitrogen( ~ 1 liter to cool the detector), and wait for ~1 hour to view the 60 keV gamma ray response (using Am 241, less than 1 µcurie) of our detector with a BNC cable to an oscilloscope. The gamma ray source can be removed from any low-priced smoke detector, available all over the world in hardware stores, and put in the center of the recess area provided in the black Delrin cap. The response will give the decay time constant of the main 60 keV pulse. It will also show the S/N ratio. The height of the pulse corresponds to a 20,000 eletron charge collected on the feedback capacitance.*

3 typical "S" or "A" models

fast medium slow

* Ge detector, gamma ray photons will produce one electron-hole pair per 3 electron volt energy. For 60 keV gamma photon energy, it will produce 20,000 eletron-hole pairs.

2. About vacuum: Repump every 6 months as required when more condensation on the cap is observed while cooling.

There is only one vacuum compartment with 2 valves. One aluminum valve is provided by Kadel Engineering. Most IR researchers know Kadel dewars and their different sizes of pumping operators. The other is in the stainless steel flange assembly, manufactured by ADC. Our old customers all have pumping operators.

We suggest that you warm up the system to room temperature and use allen wrench to open the dewar. Remove the valve insert, clean loose particles, usually on the bottom rubber disk, vacuum grease slightly the three sealing rings, install on the operator's allen screw and pull all the way in the operator body. Then slide the nut of the operator on the valve body all the way and tighten the nut on the valve while pushing the operator toward the valve.

After pumping for 24 to 48 hours with a high vacuum pump down to 1-2 x 10^-5 torr. Push the valve insert slowly in the valve and turn the handle until the valve insert is seated tightly. Remove the operator and use the allen wrench to tighten the valve insert a little more. The new small turbo pump works very well to do the pumping. We have three Varian small macro-turbo pumps.

3. Preamplifier - figures 1 & 2

Except the 2K trim pot in the 2nd stage (indicated by arrow) all the other pots are adjusted at ADC. The 2k trim pot can be adjusted by the customer to vary from 1 to 10 in the gain of the second stage.

The blue DC out, an eyelet (indicated by 2nd arrow) can be probed during operation. If it is more than +3 volt, it means the light source is too strong and the first stage is saturated. You can cover the cap with the black Delrin cap provided to see if the DC level drops to normal, 0 to -1.5 volts.

Our reserved feature of the preamplifier is labeled ACFB. It is not used. It will add extra capacitance feedback to enlarge the RC time constant. In the future, we would to find out in some applications this adjustment of RC time constant could improve the S/N ratio. It is an improvement to our very old model, which had a switch to add a fixed AC feedback to the RC time constant.

The new preamplifier box in the neck of the flange, close to the first stage inside the vacuum, is definitely an advantage to the long connecting wires, over 10 inches long, of the old model.

A crucial change in the sales effort is my personal contact. Before the sales were done by North Coast and other companies, they were reluctant to make any changes to the design. Now I will listen to every customer and answer questions I know. Although you can contact me by email - louiswang@applieddetectors.com, I prefer you call me or FAX me, so I can keeep a written record.
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Figure 1