Sunday, February 15, 2009

Solid State Photomultiplier

A company called Amplification Technologies has invented something called a solid state photomultiplier.
Amplification Technology Inc. has developed a new solid-state semiconductor technology solution for low-level signal detection: multichannel Discrete Amplification (DA).

The patented DA platform technology, invented by company scientists, is a breakthrough in the design of photon detectors, providing these detectors with unique competitive advantages. Use of DA in semiconductor detectors increases their sensitivity markedly, and enables the creation of new detector systems for various applications including medical diagnostics, security systems, telecommunications, environmental monitoring and drug discovery.
They really don't give many details of their technology but if it works as stated it could be a real boon to designers of particle detectors. The output of the device is low impedance (50 ohm) so that it should be much less susceptible to electric field noise such as is found in installations that depend on high voltage for their operation.

Tube photomultipliers, because they are high impedance devices, are notorious for their susceptibility to electric field noise. Like a photomultiplier this device is inherently high speed. The company recommends a standard microwave amplifier rated at 4 GHz for use with the device. Such solid state amplifiers are available for a dollar or two in small quantities. Pulse lengths of under a nanosecond are resolvable. In that respect their performance is similar to a photomultiplier and like a photomultiplier it can detect single photons with about the same efficiency as a photomultiplier. The gain of the device is around 1E5. Similar to that of a photomultiplier.

The question of course is: are all these improvements available at a reasonable price?

Saturday, February 7, 2009

Engineering Plan

I was having a discussion with a correspondent about how to organize a Polywell Fusion engineering program. I though I had discussed that here but it turns out that I made my remarks at NASA Spaceflight. So I would like to revise and extend those remarks.


Since I'm thinking along Manhattan Project lines I think we need a name for our little venture. I propose the "Rock River Engineering District". I don't know, it just came to me. So how should the Rock River Engineering District be organized?

We start with a project management (PM) team with representatives from each of the labs and the main functional groups. Project management is above all responsible for results. Budgets and schedules too. The job of PM is to make sure all the horses are pulling in the same direction.

Now what about project teams? Start with a power reactor group. A thermal group. An electrical group (power and control). A test reactor group. And a support group consisting of mathematicians, metallurgists, electronic design, etc. and administrative support - purchasing, contracts, etc.

The reactor group alone is going to have to have subgroups: electron guns, fuel injection, vacuum group, magnetics group, collection grid group, plasma physics. Possibly others - all working with the thermal group. Plus you want to have some mathematicians on staff for helping the engineers with the hard stuff. Reduce the engineering to algebra/trig or computer programs with graphical and table outputs.

Then you have to have some one who can ride heard on this collection of prima donnas. If they aren't prima donnas I don't want them on the program. Think Manhattan Project. Or Rickover re: nuke subs. We want very smart experienced people with an excess of confidence. With a pessimist riding herd.

I think it took the Naval reactor group from 1948 to 1953 to get delivery of the sub reactor prototype. With 6 years prior experience in low power and low power density reactors.

Wednesday, February 4, 2009

So I'm Discussing With Art Carlson

So I'm discussing with Art Carlson whether it is worth it to look deeper into the Polywell Fusion Reactor design and do some experiments with superconducting coils and continuous operation of a test reactor. Said experiments to cost about $10 million. Well Art is sure that the explanation that Physicist Robert Bussard gave for how the device works can't possibly be true and it is all just a bunch of believers. Cultists if you will. He did not hold back when expressing his views.
StevePoling wrote:
Can anyone articulate an experiment that would falsify either proposition? I mean something cheaper than building a fully-operational Wiffleball-N?
I spent some more time pondering this. I was thinking in the direction of leaving out the cusp itself and just investigating a pencil of plasma propagating along a field through hoops of various potential. Then I realized this is pointless because whiffle-ball theory is not falsifiable.

I mean, suppose I set up an experiment involving cusp physics and electric fields and I showed that it all worked as I expected. What would the polywell proselytes say? That the real polywell has (unspecified) non-Maxwellian effects that my setup didn't take into account. That is basically the last answer I got from Rick Nebel. Of course I can't refute that because nobody has ever said what those effects might be in detail. Maybe if I worked real hard for a year or so (Are there any volunteers to pay my salary?), I could prove a fairly general theorem that would rule out a large class of options. (My shining example for this type of calculation is Todd Rider.)

Basically, there is no whiffle ball theory, only some handwaving with manifest inconsistencies. On the experimental side, there is no published, robust evidence that anything unusual is happening at all. What are we doing here?
But it is falsifiable at least ultimately in an engineering way. Either you get more power out than you put in or you don't.

For $10 million we build the Super Conducting coil job and that should tell us if a power producer is possible. It should also be possible to measure the wiffle-ball. Lasers. Microwaves. Field probes. Whatever.

Or we might go with a lower cost liquid nitrogen cooled copper magnet coil version. It would have a much lower magnetic field than a superconducting coil. But you can build it faster. Vary the current through the magnet coils and see how the losses scale.

I must say though that I'm starting to feel like a tokamak guy: "there are problems that can only be worked out at the next larger level". It must be a plasma physics disease.

Tuesday, February 3, 2009

Interesting Power Supply Company

Commenter windmill at Talk Polywell has brought to my attention an interesting power supply company Diversified Technologies Inc. Here are a couple of short (under 10 pages) papers that explain the technology.

Solid State High Voltage DC Power Distribution & Control [pdf]

Here is the key point from the above [pdf].
The largest cost components in this design are the semiconductors (IGBTs). Because of their widespread use in locomotive engines, subway cars, elevators, and a wide range of electrical motor drive and power supply systems, these devices are evolving at a rapid pace, especially in comparison with vacuum switch tubes. In the last decade, we have seen the switching speed and power handling capability of IGBTs increase by an order of magnitude (200 kVA to 4 MVA), at essentially constant prices. This puts high power electronics, for the first time, on a favorable, long term cost reduction path. This is the equivalent of the computer industry’s Moore’s Law of continually higher performance per unit cost, but applied to power systems.

Today, a 100 kV, 2MW buck regulator, with a series switch, can be built for approximately $500k USD. This cost will decline due to increased semiconductor performance and decreased manufacturing costs. In contrast, estimates for the equivalent conventional approach are $2- 3M USD, and show no trend towards cost reduction.
Quite so. IGBTs with a voltage rating of 6,500 Volts and a 600 Amp current rating are now off the shelf.

A Solid-State Switch for 13.8kV Power Distribution [pdf]

The company claims to be able to make power conversion equipment that costs in the range of 10¢ a watt in production quantities. That is a very good number. Diversified claims specifications for their supply technology that are very not too bad. An adjustable 100 KV DC supply can deliver 1% regulation and .1% ripple. That is just the ticket for Polywell Fusion experiments using D-D. For pB11 at the resonance peak I'd like to see tighter regulation. Say .1% regulation and .01% ripple. I have some ideas.