How Do You Detect A Neutrino?

Another Don Lincoln video, and this time, it is on a topic that I had a small involvement in, which is neutrino detection.



My small part was in the photomultiplier photocathode used for detection of Cerenkov light that is emitted from such a collision between the "weak boson" and the nucleus. We were trying to design a photodetector that has a large surface area as compared to the current PMT round surface.

In any case, this is a good introduction to why neutrinos are so difficult to detect.

Zz.

Gamma-Ray Imaging At Fukushima Plant

I mentioned earlier of the muon tomography imaging that was done at the damaged reactor at Fukushima, and tried to highlight this as an example of an application that came out of high energy physics. This time a gamma-ray imaging spectroscopy was performed at the same location to pin-point contamination sites.

But as with the muon tomography case, I want to highlight an important fact that many people might miss.

To address these issues of existing methods and visualize the Cs contamination, we have developed and employed an Electron-Tracking Compton Camera (ETCC). ETCCs were originally developed to observe nuclear gammas from celestial objects in MeV astronomy, but have been applied in wider  fields, including medical imaging and environmental monitoring.

So now we have an example of a device that was first developed for astronomical observation, but has found applications elsewhere.

This is extremely important to keep in mind. Experimental physics often pushes the boundaries of technology. We need better detectors, more sensitive devices, better handling of huge amount of data very quickly, etc...etc. Hardware have to be developed to do all this, and the technology from these scientific experiments often trickle down other applications. Look at all of medical technology, which practically owes everything to physics.

This impact from physics must be repeated over and over again to the public, because a significant majority of them are ignorant of it. It is why I will continue to pick out application like this and highlight it in case it is missed.

Zz.

Detecting Particles By Seeing Them Move Faster Than Light

No, this is not a topic on superluminal particles. Rather, it is an article on how we detect particles by using faster-than-light particles in a medium, i.e. by observing the Cherenkov radiation.

But photons only move at that perfect speed-of-light (c) if they’re in a vacuum, or the complete emptiness of space. Put one in a medium — like water, glass, or acrylic — and they’ll move at the speed of light in that medium, which is less than 299,792,458 m/s by quite a bit. Even air, which is pretty close to a vacuum, slows down light by 0.03% from its maximum possible speed. This isn’t that much, but it does mean something remarkable: these high-energy particles that come into the atmosphere are now moving faster than light in that medium, which means they emit a special type of radiation known as Cherenkov radiation.

The article listed several detectors that make use of this effect, but it is missing A LOT more. Practically all neutrino detectors use this principle (i.e. SuperKamiokande). Auger Observatory also looks out for these Cherenkov radiation.

But the part that I think should fascinate the layperson is when the speed of various things are listed, up to the most accurate decimal places:

It’s true that Einstein had it right all the way back in 1905: there is a maximum speed to anything in the Universe, and that speed is the speed of light in a vacuum (c), 299,792,458 m/s. Cosmic ray particles can go faster than anything on Earth, even at the LHC. Here’s a fun list of how fast various particles can go at a variety of accelerators, and from space:

• 980 GeV: fastest Fermilab proton, 0.99999954c, 299,792,320 m/s.
• 6.5 TeV: fastest LHC proton, 0.9999999896c, 299,792,455 m/s.
• 104.5 GeV: fastest LEP electron (fastest accelerator particle ever), 0.999999999988c, 299,792,457.9964 m/s.
• 5 x 10^19 GeV: highest energy cosmic rays ever (assumed to be protons), 0.99999999999999999999973c, 299,792,457.999999999999918 m/s.

 Just notice how much energy we had to put in to, say, the proton in going from 0.99999954c to 0.9999999896c. And then, notice how high of an energy cosmic rays have when compared to the LHC. If these types of collisional energy can create "catastrophic blackholes", we would be gone by now, thankyouverymuch!

Zz.

"Fart Detector" Wins Chinese Physics Prize

OK, there are many aspects this story.

When I first read the title, I honestly read it as "Fast detector", which is reasonable, because fast detectors are useful. But when I read it again, I did a double take. So of course, I had to open the link to the story and figure out what this is.

Turns out that that wasn't the original intent of this detector. Rather, it is trying to sniff any odor in a moving air and to locate the source. Of course, the media, even in China, took it to its most obvious "application" such as sniffing (pun intended) the source of a fart. Question is, what do you do when you find the culprit? Is it unlawful in China for someone to fart in public? Do you shame this individual for such an act?

Finally, it turns out that the prize given is the "Pineapple" prize because "...the fruit which in China is said to be so ugly that only the brave and curious would explore its delicious interior..."

Whaaaaaat????!!!!

I guess this is another example of beauty in the eye of the beholder. I had never, even a second, consider the pineapple to be an "ugly" fruit. In fact, if you've been in to Hawaii or the tropics (especially in South East Asia where the fruit is abundant), it is considered to be beautiful enough to be used as decorations!

In any case, I don't think this research work is "useless" to even qualify for an Ig Nobel prize.

Zz.

The Detectors at the LHC

Don Lincoln has a video on the 4 detectors at the LHC.



As you watch this, don't miss the fact that these are "... technological marvels..." in themselves, and that high energy physics had to invent and make their own detectors and detection processes to advance the field. Detector and instrumentation physics have always been an integral part of experimental high energy physics, and one often sees students in this field that are actually working on detector physics.

As a consequence, high energy physics drives innovations and new applications that eventually leaks into the rest of the world. This is a point that is often missed by those outside of the field.

Zz.

2014 Ig Nobel Prize

As usual at this time of the year, the Ig Nobel Prizes has been awarded to a group of really serious but fun/useless/trivial/etc work. The award for physics this year is on the study on how slippery banana peel really is.

Physics: A Japanese team has finally tested whether, indeed, banana skins are really as slippery as slapstick comedy would have us believe. In “Frictional Coefficient under Banana Skin,” they show a banana skin reduces the friction between a shoe sole and the floor by about a fifth. 

But what caught my eye was the award given for Neuroscience, which I don't think is that trivial or useless.

Neuroscience: In “Seeing Jesus in Toast,” a team from China and Canada have clinched the neuroscience prize with an exploration of a phenomenon called face pareidolia, in which people see nonexistent faces. First, they tricked participants into thinking that a nonsense image had a face or letter hidden in it. Then, they carefully monitored brain activity in the participants they managed to convince, to understand which parts of our minds are to blame.

This is, actually, quite important in arguing against people who rely on "seeing" with their eyes as a primary source of evidence, which are often part of an anecdotal evidence.

I argued before on why our eyes are really not a reliable detector. That post came about because I've often been questioned about the validity of the existence of an electron simply because we haven't "seen" it with our eyes. I put forth a few facts on why our eyes is really a rather bad standard to use in detecting anything simply due to the limitations it has on a number of properties.

This paper about seeing Jesus in toast is another solid point to add to those arguments about us "seeing" something. It adds to the fact that we do not just see something, but also PROCESS the optical signal from our eyes via our brain. Our brain, due to either conditioning, evolution, etc., has added these filters, pattern recognition, etc. to help us interpret what we are seeing. And it is because of that that we have the potential to see something that isn't really there. This work clearly proves that!

It is another reason "seeing" with our eyes may not always be a reliable evidence.

Zz.

Physics In Health And Industry

I always try to show people that many of the stuff they now use, came out of the research work that had almost no apparent and immediate practical application. I often use high energy physics as an example, because in many camps, this is the poster child of esoteric physics that has no clear applications. Yet, people forget that the World Wide Web, the medical detector and diagnostics, and many others, came about as direct spin-offs of experiments in high energy physics.

This report of a recent conference on advanced radiation detectors will reinforce this point.

The first afternoon was rounded up by Colin Latimer of the University of Belfast and member of the EPS Executive Committee. He illustrated the varying timescales between invention and mass-application multi-billion-dollar markets, with a number of example technologies including optical fibres (1928), liquid-crystal displays (1936), magnetic-resonance imaging (MRI) scanners (1945) and lasers (1958), with high-temperature superconductors (1986) and graphene (2004) still waiting to make a major impact. Latimer went on to present results from the recent study commissioned by the EPS from the Centre for Economics and Business Research, which has shown the importance of physics to the European economy.
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Erik Heijne, a pioneer of silicon and silicon-pixel detectors at CERN, started by discussing innovation in instrumentation through the use of microelectronics technology. Miniaturization to sub-micron silicon technologies allows many functions to be compacted into a small volume. This has led in turn to the integration of sensors and processing electronics in powerful devices, and has opened up new fields of applications (CERN Courier March 2014 p26). In high-energy particle physics, the new experiments at the LHC have been based on sophisticated chips that allow unprecedented event rates of up to 40 MHz. Some of the chips – or at least the underlying ideas – have found applications in materials analysis, medical imaging and other types of industrial equipment. The radiation imaging matrix, for example, based on silicon-pixel and integrated read-out chips, has many applications already.

Without the effort and the need to push the capabilities of these detectors, there would be no reason to innovate, and the pace of advancement in many of these detectors will slow down considerably. The need to make better detectors to do high energy physics experiments DRIVES innovation in these various areas that have a clear and direct spin-offs into practical applications.

This is the part that many, including politicians, seem to not be aware of.

Zz.

Single-Photon Detectors

This topic came up a few times during the past month in online discussions and with a few people that I've met. Most of these were in context with the photon detectors used in the EPR-type experiments, but a few came up due to the photon detectors used in detecting Cerenkov light from neutrino experiments.

A lot of people are confused with, and misinterpret, the meaning of "single-photon detectors". Most of them who are not familiar with it think that such detectors can detect every single photons that the detector comes in contact with, i.e. if there's a photon hitting a detector, it will detect it.

This is false. A single-photon detector is sensitive down to detecting single photons. So this is a sensitivity issue. However, it doesn't mean that it has a 100% efficiency. It doesn't detect every single photons that it encounters.

A photodetector such as a photomultiplier tube used in many photon detector is often made up of a photocathode (it converts the incoming photon into a photoelectron), an electron amplifier (something that multiply that single photoelectron into many electrons), and a signal generator/converter that converts the many electrons into an electrical signal. This is what we eventually detect in our electrical signal.

The problem here is that the photocathode does not have a 100% quantum efficiency. In fact, most photocathodes used in photodetector tubes have quantum efficiency less than 50%. What this means that if 100 photons hit the photocathode, less than 50 of them will be successful in generating a photoelectron each. The rest of the photons that hit the photocathode will generate no photoelectron and are lost.

So while the detector is sensitive down to the single-photon level, it is not 100% efficient. Single-photon detectors refer to the sensitivity, not the efficiency, of the detectors.

Zz.

Graphene - The Aspirin Of Microelectronics

A while back, aspirin was touted as a miracle drug. Its use beyond just being a pain killer was being discovered constantly, ranging from an efficient blood thinner to prevent heart attack and stroke.

That is why I'm calling graphene as the aspirin of microelectronics. It seems that almost every year we hear more and more use of this miracle material. It's a good conductor, it is very strong, and now, in the latest chapter of what graphene can do, it has been touted as a very efficient converter of light into electricity.

Now the one-atom-thick lattice of carbon has added another string to its bow. Three research groups have independently shown that graphene can efficiently convert infrared light into electrical signals, as part of devices known as photodetectors. As fast and accurate translators of optical data, graphene photodetectors could speed up computers and significantly cut their power consumption. The devices, each with a slightly different architecture, are reported in Nature Photonics.

This performance already rivals that of existing photodetectors. “We’re seeing graphene getting to a point where it can compete with today’s technologies,” says Dirk Englund, a physicist at the Massachusetts Institute of Technology in Cambridge who developed one of the graphene photodetectors. “That’s an important new step.”

I expect it to be able to clean windows soon.

Zz.

Particle Physics Is Worth Funding

I wasn't going to comment on this article, but I decided to anyway.

This appears to be an opinion piece for a college newspaper at Oklahoma University. It has some minor issues that do not detract from the central message of the article. The author is presenting a case on why something as esoteric as particle physics is worth funding.

Sounds interesting, but laypersons are not amateur physicists, and want to know the practical benefits of what their dollars are funding.

The difficulty with this reasoning is it ignores how the nature of science operates. Albert Einstein did not anticipate his theories of relativity would play a prominent role in GPS satellites and smartphones. The discovery of quantum mechanics, perhaps the most esoteric of the sciences, would ultimately give rise to conductors and computers. Virtually all of electricity can be traced to research conducted in the 19th century that was thought to have little, if any, practical benefit. Many of the machines found in hospitals such as MRI’s are based upon principles of physics discovered by physicists who had no interest in medicine. In order to properly do science, even the most abstract subjects need and deserve funding.

This certainly is true, and a message that I've posted here many times.

The minor issues I have with this article are:

(i) the technical aspects of it, especially when he said" ... The discovery of quantum mechanics, perhaps the most esoteric of the sciences, would ultimately give rise to conductors and computers..." when I think he meant "semiconductors". The discovery of QM did not give rise to conductors, because we already know about Ohm's law and everything else about conductors well before QM was formulated. We even know about semiconductors before then. We just don't know the physics of semiconductors.

(ii) the "references" being used are often other news articles. This is fine IF you are commenting on that news article (like what I often do in this blog). But if one wants to have proper citation to back one's claim of either science or a fact, using a news article is equivalent to passing on a piece of gossip. We have seen how news articles can often skewer something, or even get it totally wrong. So not a good idea to depend on such sources to justify one's opinion.

There's also something interesting here. The article is written by a philosophy major. On one hand, it is too bad someone with a physics background (a physics major) did not write this. I mean, who else is more qualified to try and sell to the public why they would fund what they do? I'm guessing such a person would not commit the two issues I listed above. But on the other hand, having someone else trumpets the importance of what we do, someone without a direct financial, vested interest, might carry more weight. Having a non-physicist urging for support for particle physics might certainly be a novel effort that might get more attention. I don't know.

The article missed a few other important reasons why particle physics is worth funding. I mentioned one important aspect of it earlier where particle/high energy physics experiments drives innovation and technological advancement in the area of detectors. Again, it is worth repeating that while most other areas of science construct and design their experiments based on equipment that they can buy commercially or that are available on hand, high energy physics often can't do that. This is because many of the detection and things they want to do, and the accuracy/resolution/speed that they need, have not been invented. So what they end up doing is to innovate and invent their own devices and detectors. This innovation and technological advancements eventually trickle down to other areas of physics, science, and the general population. And this area of detectors is just one example. One only needs to look at their computing needs and how much data they have to handle to know that they are also doing unbelievable innovation in terms of data transfer, handling, computing needs, etc. Don't tell me other companies are not observing and learning from this very carefully.

And speaking of detectors, if you wish to further check up on my claim of particle physics innovation in this area, check out the proceeding from the 2nd International Conference on Technology and Instrumentation in Particle Physics (TIPP 2011). Papers are available for free. Bookmark it. I can guarantee you that a few of these that were designed for particle physics experiments will directly impact our lives in the next decade when they are used in other instruments.

Unfortunately, here in the US, funding for high energy physics continue to decline. The impact on this to the US intellectual activities, innovation, and economy can only felt once it becomes too late.

Zz.

High Energy Physics Drives Innovation And Technology

I want to bring one ONE very specific example of how high energy physics is driving advancement in a certain technology that WILL have huge impact later on in many parts of our lives.

This report shows the drive for larger, faster, and more importantly, cheaper photodetectors. This was driven by the needs in particle physics detection, especially for the Cerenkov light detection from neutrinos. Current technology is based on photomultiplier tubes and is dominated by almost a single-source supplier - Hamamatsu. And you can imagine, these photomultipliers are prohibitively expensive, especially the ones with higher light detection efficiency. But these PMTs also have "round" cross-section, and in some cases, will have coverage that are not very high.

All of these factors affect the light detection from such high energy physics experiments, and thus, the demand for better detection from such experiments are driving the need for new, better, and cheaper detectors. It is the driver for new innovation and technology, which is what high energy physics does all the time! They often have to build and invent their own detectors each time they build bigger and better colliders!

And guess what? We will benefit from such innovations! The technology invented with the photodetector described in the article will have a myriad of benefits. There are already discussion on the applicability of this technology for PET scanners. In this case, being large, cheap, and fast are three characteristics that are highly desirable.

So if you want to follow the development of something in "real time" as an example on how a demand in high energy physics eventually translates to something that you and I benefit from, here's one that you can track as it happens. The folks at R&D 100 obviously are already aware of the enormous potential for this one.

Zz.

Seeing Is Over-Rated, Part II

I wrote earlier on the limitations of the human eye, and why it makes for a very poor photodetector, when compared to other photodetectors that we currently have. The earlier blog entry dealt with the response bandwidth of the human eyes, and the quantum efficiency.

This time (no pun intended), we will deal with the response time, which will produce the time resolution, of the human eye. We all know that when we go see a movie, it is nothing more than a series of still-image frames, moving past us fast enough that we do not see its motion, but rather see the image as being continuous. Standard movie frames (at least till all the new advancements in movie projection) used to go at 24 frames per second (FPS). This translates to 0.04 second per frame. We also know that the human visual system holds an image for about 0.02 second. It means that anything that comes into our visual system faster than 0.02 second will not be perceived as being distinct. So the 0.02-0.04 second is roughly the time resolution of the human eye.

Now, compare this to other devices. I've listed before some typical photocathodes used in accelerators. Note the time responses for the various types of photocathodes. The worst of these are in nanoseconds. This is still order of magnitudes shorter than the human eye! One example is GaAs, which is a common photocathode use in both accelerators and photodetectors. On Pg. 25, one can see measurement of the time response. The full-width-at-half-maximum of this photocathode is of the order of picoseconds!

So the human eye is not only a bad detector in terms of its bandwidth range and also in terms of sensitivity, it is also a very SLOW detector and can't separate a series of event occurring faster than 0.02 second!

Zz.

"Seeing" Is Over-Rated!

I lose track of how many times I've heard an argument against something in physics because "we can't see it". I've even heard an engineering professor once argued with a student about electrons by asking the student "Have you seen an electron?". This issue came out again in light of the recent news flurry about the apparent discovery of the Higgs, and some moron somewhere continues to belittle high energy physics, and physics in general, about imagining such particles that we "can't see".

Of course, there are several ways to attack such stupid (yes, STUPID) arguments. The first is the question on what we mean by "seeing". Often, most people simply meant seeing something with the human eyes. But what exactly does that mean? If these people were to think carefully, it means a series of events that must occur: (i) visible light from some source hits an object; (ii) light from that object travels to our eyes (iii) our eyes then transmit electrical impulses to our brain (iv) we detect that object visually. That, my friends, is what is meant by seeing with our own eyes.

Next, by the above description, it is clear that our eyes can only see electromagnetic radiation, and not only that, it can only see it within the visible spectrum, which isn't very much. Thus, if something either does not emit EM radiation, or if the radiation is outside of the visible spectrum, we can't see it! Let's go back to our friend the electron. It is a charge particle. Our eye cannot "see" it even if it hits our eyeball! But can we still see it? Sure we can! Enter a cloud chamber! When an electron, especially high energy ones, moves through a cloud chamber, it ionizes some of the air/gas/water vapor molecules. This creates a nucleation site for water vapor condensation, leaving a cloud trail in the chamber. There, you have seen an electron. One could also argue that our eyes are not the only "detector" around. We can also use our other senses. We can't see wind, but we can hear and feel the moving air. We can't see heat/IR, but we can certainly feel it on our skin. Our eyes is only ONE of the "detector" that came with our bodies.

And speaking of the human eyes as detectors, anyone who has done anything with detection instruments can tell you that the eyes is a very bad detector in many cases. Sure, it has a very high spatial resolution, but man, it sucks everywhere else. For example, look at this figure that shows the sensitivity of the human eye over a range of frequency and also its response sensitivity.

Compare to other devices, the human eye has 2 very clear shortcomings: (i) the range of wavelength it is responsive to is extremely small; and (ii) its sensitivity (i.e. quantum efficiency, or QE) is quite low. It has a peak QE of ~1% at around 550 nm. What this means is that out of 100 photons that come in, it can detect, on average, only 1. Compare the range and QE of Vidicon and CCD and our eye is a very poor light detector! And this is what some people are using as the sole criteria of what's real and what isn't? Is this rational?

As with many things that a lot of people spew without thinking, the debunking of such things often are quite simple IF one has a little bit of knowledge, and the the ability to analyze the situation. Analyze what it means by "seeing", and then analyze the "detector" that is being use as the criteria. And apply such techniques to the pile of manure that one often hears in the media from politicians, etc., assuming you have such patience.

Zz.

Possibility of LHC Data Pile-Up

Too  much of a good thing is not necessarily a good thing.

So they want a lot of collisions, now they might get too many to handle. The detectors at LHC are preparing for the possibility of data pile-up, now that the LHC is operating at a higher energy and higher luminosity than what the detectors are designed to handle.

Every time two tightly packed bunches of protons cross, they generate not one collision, but on average 27, Lamont says. But within a few weeks, that number is expected to rise into the mid-30s, peaking at around 40 collisions per crossing. The two main detectors at the LHC were designed to handle only around two dozen collisions at once. But they have managed to cope so far.

While this is a good problem to have, it is still a problem, because you simply don't want to have to discard something simply because you can't handle it. It appears that they can, so far, but I can easily see that this number will continue to increase. Considering the daunting size and what they are trying to do, the LHC continues to be an astounding machine that is performing incredibly better than expected.

Zz.

PVC Extrusions For NOvA

{Don't miss our nomination period to nominate your most attractive physicists}

I pointed out a video of the assembly of the prototype NOvA detector a while back. This is a picture of the cross-section of the PVC extrusions that make up the detector block.

The channels formed by the extrusions will be filled with scintillator liquid (mineral oil?) that hopefully will emit light when a neutrino interacts with the liquid.

A lot of studies have been done with huge structures of these PVC, especially on its structure integrity for something that size over a period of time. In any case, the NOvA detector will have its ribbon-cutting ceremony sometime later this month, and construction will commence very soon afterwards.

You may read more about the NOvA project at their website.

Zz.

Assembly of Prototype Blocks for NOvA Detector

For those who don't get to see the "behind the scenes" of all the hard work that goes into constructing some of the stuff that we want to do, here is a video of one such endeavor. This is the assembly of the prototype NOvA detector prototype that will eventually be employed at Ash River in Minnesota. It took a lot of engineering effort to come up with not only to come up with the design, but also to figure out how to properly assemble these detectors at the remote site.




A little bit of insight into this video. This testing was done at Argonne National Lab. They assembled and tested it under the High Energy Physics division's effort. What they didn't mention in the video is that the "glue" that they used to assemble the detector STINKS TO HIGH HEAVEN! :) :) I've always wanted them to actually use the glue each time we have high-level visits by some administrators from DOE or somewhere, so that these people can smell the stink! But I suppose that would be bad form. :)

Zz.

"Detectors for Future Colliders"

Hitoshi Yamamoto from Tohoku University is talking about this topic in the plenary session of TIPP Conference (last day).

He talks about the LHC upgrade for the detectors. They are designed to work at 1e34/cm^2/s luminosity, but there are many issues for detectors under such conditions. He talks about the ATLAS, CMS, ALICE, and LHCb upgrades during the various planned LHC shutdowns.

SuperB Factories - KEK has luminosity of 2e34/cm^2/s. SuperB factories will have 40-50 times more luminosity. He describes the requirement for SuperB detectors.

Belle II upgrades are also mentioned.

ILC is next. Detector performance goals for ILC are described. The ILD detector has a B field of 3.5 Tesla, while the SiD detector has B field of 5 Tesla.

He then describes requirements for CLIC and Muon collider detectors. The 1.5 TeV version of the muon collider detector will have challenging beam background.

Zz.

"Gravitational Wave Detection"

More from the ongoing TIPP conference. Sam Waldman from MIT is presenting this topic during the morning plenary session.

The talk covers the effort in detecting gravitational wave.

"Mass tells spacetime how to curve, and spacetime tells mass how to move" - Wheeler

Astrophysical tools to produce gravitational waves - neutron stars and black holes. He is showing a movie of two compact stars orbiting each other, and also had an audio of the frequency change as the two stars collapse into each other.

Zz.

"Improved PMTs for the Cherenkov Telescope Array"

A talk at the TIPP conference going on now in the Photon Detector session. This one is presented by Razmik Mirzoyan of Max Planck Institute. It's a fascinating look at what can already be achieved now for the CTA effort, and a hint of what might be possible in the future simply based on existing technology.

The core people in the CTA are MAGIC, HESS and VERITAS collaborations. It is an initiative to buld the next generation of large ground-based gamma ray detector, with 10 times higher sensitivity. They want to study AGNs, Black holes, gamma ray burst, and galactic sources (pulsars, supernovae, etc. Energy range is from 10 GeV to 100 TeV. Try to answer long-standing question about origin of cosmic rays. Planning on ~100 telescope, 2-arrays (south and north pole).

3 types of telescopes are planned, Large: 23 m, midsize 12 m, and small 4-7 m diameter. Use standard PMTs and maybe SiPM.

PMTs mainly from Hamamatsu and Electron Tubes, with QE peaking around 35-40% at around 400 nm. He selected the 1.5" PMT and discussed at length the property of the PMTs from the two companies. These are the ones being considered for the CTA, I presumed, if not used already.

Zz.

TIPP Conference, Day 2

Attending the TIPP 2011 conference. Great plenary session this morning. A very concise review of neutrino detectors and experiments, and what experiments are in the pipe line in the future. Then there were talks on Dark Matter detection, both "direct" and "indirect".

The detection process itself is a major field of study, and another area where engineering and physics merge.

This promises to be a very long day of very interesting talks, especially in the afternoon when there are several parallel sessions.

Zz.