SensL SiPM Availability for Cosmic Watch

New info: SensL was aquired by ON Semiconductor, and SensL no longer sells products from its site; it is currently not know what this may mean for the special purchase price that had been offered to researchers and students building the MIT Cosmic Watch. The sensor as used in the Cosmic Watch most likely will still be available, but the price may be higher.

I am looking into this to see if the special price or something similar can still be offered to high school teachers and others involved with teaching or learning/project/research. It’s possible that we could get an even better price from ON, being a larger multinational semiconductor corporation — which, if ON Semiconductor is listening, would be fantastic for teachers and students.

Their notice:
Effective on Tuesday October 23, 2018 at 4:00 PM GMT the SensL eStore will no longer accept orders.
Starting Monday October 29, 2018 you will be able to order from a wide range of worldwide distributors.
Please visit this website for the complete list in your region:

Happy Higgs Day from CERN!

Six years ago I stayed up all night to watch the announcement from CERN that was rumored to be about the Higgs boson. I ordered a particle physics textbook that night, having never taken a formal class that went beyond a general historical approach.

Particle physics had always sounded interesting. I increased my participation in QuarkNet, brought particle physics into my physics classes for my students, and a year later I spent a week studying at Fermilab.

Now, six years later, I attend lectures in the very hall where CERN scientists broadcast their discovery to the world, learning from scientists involved then and now in pushing the forefront of knowledge in physics.

I have had the good fortune to spend five of the last six summers working with scientists and students at KU doing particle physics research and projects.

And I have had the immense fortune of meeting many physics teachers around the US and the world who share a passion for physics, learning, and teaching.

I could not have dreamed twelve years ago when I started my teaching journey what amazing opportunities I would find. I’m a little more in awe of it every day. And while this (first?) visit to CERN seems like a pinnacle of experience, I can’t help but wonder what the next six years could bring.

Happy Higgs Day!

Building a new Cosmic Ray Detector

For the past five years I have been fortunate to have a QuarkNet cosmic ray muon detector to use for teaching and for research with students. It’s a fun piece of real particle physics hardware, and lets me and my students go hands-on with the same muon-tracking tech we see at Fermilab, CERN, and other facilities.


QuarkNet Series 6000 CRMD. Photo: QuarkNet/Fermilab


One of the limiting factors preventing more teachers and students from using these detectors is their high cost. Without QuarkNet making these available for us to borrow, these detectors would cost us several thousand dollars each.

In the past few years I’ve seen projects to detect cosmic rays in a variety of ways, notably CRAYFIS and DECO that use the silicon imaging chip in your phone’s camera when the lens is covered or in a very dark environment. This method uses techniques similar to the silicon detectors like the pixel and strip trackers in the CMS detector at CERN. One disadvantage is the tiny area and volume of that phone sensor chip, which probably intercepts less than one muon per minute.

A more promising route for classroom use is the MIT detector, called the Cosmic Watch. This project uses inexpensive hardware to bring higher level, scintillator based cosmic ray muon detectors to teachers and students for a target price of $100, about 98% less than the absolute cost of the more capable QuarkNet detector.


Cosmic Watch CRMD. Photo:

I’m in the process of acquiring the components to build a Cosmic Watch, starting with the silicon photomultiplier from SensL in Ireland. They were kind enough to offer the preferred detector chip in small quantities to students and teachers for a discount price of $60 with available $15 shipping (no word on how long they will run this discount).


Mounted SenseL SiPM. Photo: SenseL

The MIT Cosmic Watch project website and Git repository include all of the information you need to build the detector, including source files for having the PCBs produced, dimensions for the scintillator, parts lists, and instructions for assembly and use. [2/20 Note: The newest version, which includes microSD capability and coincidence capability with two units and other revisions, can be found at the v2 Git repository here.)

Future posts here will discuss the similarities and differences between the QuarkNet and Cosmic Watch detectors, including sensitivity, data collection process, and coincidence signal detection.

Right now I’m simply going to build one for myself to experience the build and learn more about it. I’m thinking maybe local teachers would be interested in a build workshop to put together, test, and take home their own Cosmic Watch. Watch here for updates — I anticipate building this over spring break (March 17-25).

KU QuarkNet Week 2-3: Research Underway


Research Projects

The QuarkNet research assistants, all high school students or 2016 graduates, are hired to work in the Department of Physics and Astronomy. During this time, they are working with professors, graduate and undergraduate students, and others to contribute to ongoing research projects at the University.

Photos and Descriptions


Brittany and Ardrian jumped into assembling the QuarkNet Cosmic Ray Muon Detector.


Prof. Besson advises returning QuarkNet researcher Margot.


Sabrea, Asher, and Roxanna (seated) learn to operate and analyze the data from radio transmission and reception experiments.


Sabrea, Asher, and Roxanna (seated) learn to operate and analyze the data from the radio transmission and reception experiment.



Ardrian and Brittany find that commissioning a Cosmic Ray Muon Detector requires lots of testing, careful assembly, and light-tight tape.


Bennett, Margot, and Pierce collaborate on research. All three are returning QuarkNet researchers.


Within a couple of days, Ardrian and Brittany had the detector functioning and under test.



A particularly well-timed photo of Bennett and Pierce testing the revisions to their lightning detector, begun in the 2015 research season. Their device(s) are part of the TARA research at KU.


Bennett and Pierce delivered a preliminary talk about their research work and the hardware they have created to generate a trigger that includes directional and range information.


The audience at a typical research seminar includes professors, graduate and undergraduate students, and fellow QuarkNet research assistants.

QuarkNet is funded by grants from the Department of Energy and the National Science Foundation.


Makerspaces in Classrooms

I ran across a listserv post I made about a year ago, and it’s something I still think is important. This was in response to a post about converting a classroom into a STEM lab. Here’s my thoughts with only minor edits:

I would recommend perhaps trying to make that STEM lab a full

​Make it a place where your community (students AND teachers) are welcome
to come learn how to use different tools to create, make, invent, and
experience things. I have done something like this with a very small corner
of my classroom, and while the supplies and topics are limited it does give
me a place (and resources) to teach an interested student how to solder,
test electronics, and build projects.

The Maker movement is not limited to any one technology, nor is it just
STEM.​ The new acronym STEAM incorporates the arts, and I believe that
creating Makerspaces/Hackerspaces in schools could be a step toward
reuniting the creative disciplines of science, engineering, and the arts.

With a properly equipped makerspace you could then offer, or could find
people to offer, seminars on woodworking, digital circuit design, robotics,
3d design and printing, fabric crafts and working with sewing and
embroidering, incorporating microcontrollers and programming in artistic
and fashion projects, woodworking, analog circuits, clay sculpture,
microcontroller programming, game programming, jewelry, crafting musical
instruments, creating analog and digital effects circuits (pedals) for
electric guitars…obviously I can’t list everything here.

Make it a space that is open, welcoming, and useful to people interested in
science, engineering, math, and arts.  Cooperate with the art, music, tech
ed, and other teachers to try and bridge the imaginary gap between the

R​esource​s​ you might look at:


New Science Facilities

Our community recently approved a bond issue to, among other things, replace our 1960’s era science classrooms. They are poorly equipped and woefully small.

I have been keeping a “wish list” to share with the architects and engineers during our consultations between now and the end of construction. We break ground in the spring.

Physics teachers, what classroom features, bulit-ins, and equipment would you consider essential to include in a new facility? What would be on your ‘wishlist’?

Please comment below and/or reply on twitter to .

Spontaneous Calculation

Sometimes the most fun in class is when it skews off in a wildly unplanned direction.  Sometimes it’s a big skew, sometimes a little detour.

We have been studying particle physics topics in class for the past couple of weeks, including a trip to Kansas State University for a QuarkNet Master Class.  We were discussing in class that the data we used to determine the mass of the top quark came from the Tevatron at Fermilab, and that it was from a proton-antiproton collision.

Some of my students were a little incredulous at the thought of antimatter, asking “Isn’t that a science fiction thing?”  Yes, yes it is, but it is also very real.  There just isn’t much of it around, and that why exactly we have almost exclusively matter and no antimatter is a Really Good Question We Haven’t Solved Yet.  Although there is no significant amount of antimatter naturally occurring anywhere in the universe, such as no antimatter stars or planets or nebulae that we are aware of, we can manufacture it.

Manufacture it?  Yes, we can.  Particle colliders like the LHC do it all the time.  It is even created naturally in tiny quantities through certain types of radioactive decay.

“So,” one of my students asked, “how much would a pop can full of antimatter cost?”


That is a good question that deserves an answer.  After mentioning that I’m pretty sure we have not produced a pop-can full of antimatter of any kind in total, I was off to find the answer.

A Google search quickly came up with a NASA site from 1999 that quoted the cost of antihydrogen at $62.5 trillion per gram.  Sure, that’s 1999 dollars, but it will work for our purposes.

We needed a few other factors, like the density of liquid hydrogen (70.99 g/L), and the conversion from 12 fluid ounces to liters (12 Fl.oz. = 0.354882 L).  And with a quick calculation, we had our answer:  $1.57E15

That’s $1,570,000,000,000,000.

Over one and a half quadrillion dollars.

The discussion swayed to how many pop cans of antimatter you could buy if you could sell the entire planet, but by then the period was winding down and it was time to go.

It leaves me wondering…by the end of my teaching career, how far that cost for a pop-can full of antihydrogen might fall.