With her picture on a dime...
Sep. 25th, 2010 09:16 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
pheloniusfriarI just registered for the Canadian Undergraduate Physics Conference in Halifax (Oct. 21st through the 25th). This will be my first trip to Canada's east coast, and I'm really looking forward to it! It's been my goal since I've been back to get somewhere out that way sometime, and sooner than later is better :). I have been up and down much of the US east coast (Florida, Georgia, North and South Carolina, Virginia, Maryland, Massachussets, and Maine), but never in Canada. I will be presenting a talk entitled "Using Cosmic Ray Muon Tomography to Detect Concealed High-Z Materials" based on the academic research and engineering work I've done since January this year at Carleton University. I'm nominally paying my own way, but there is murbling that at least most of the conference registration cost will be reimbursed by Carleton after the fact (if not my transportation to and from Halifax). The conference fee ($350) is pretty "all inclusive": accomodation at the swank Lord Nelson Hotel for 4 nights, breakfasts, lunches, transportation to/from the pub crawl Friday, a harbour cruise Saturday evening ($15 extra), a banquet dinner on Sunday. I think I just need to cover dinner for 3 nights and the cost of booze ;).
The abstract that I submitted for the talk is:
Here are a couple of pictures of the system as it stands (three more chambers are being built). This is a working cosmic ray telescope. What's interesting is that it's a project that would be within the abilities of a home hobbyist to design and build. I'm thinking about maybe trying to get the Physics Society at Carleton to start on a project to design and build a smaller system and then maybe publish the plans in Make magazine or something :).
This is the overall setup, with the telescope on the right, the scintillator electronics and high voltage (about 12kV) supplies in the middle, and the data acquisition system on the left (I was responsible for the scintillator electronics and the data acquisition system and programming):
This is a side view of the muon detector. It is a layer of scintillators on top, a “drift chamber” (it has the layers of blue foam that are visible from the side), another layer of scintillators right under the chamber (hard to see), a layer of lead (wrapped in brown paper), and another layer of scintillators near the floor. A particle or photon (e.g. x-ray or gamma ray) has to travel through all three scintillators before it's accepted as a valid “event”. The lead (about 6cm or so) blocks just about everything but muons, which don't interact with matter particularly much (they just bounce off the electron shells of atoms until they run out of speed and decay into electrons/positrons and neutrinos). Muons are produced when cosmic rays (ultra high speed protons and helium nuclei) smash into atoms in Earth's upper atmosphere. They only live around 2.2us, but survive the trip from the upper atmosphere to the ground because they are travelling at almost the speed of light and experience significant time dilation because of that (they only “see” the atmosphere as being a couple of thousand feet thick, and so it's not that far to them). Anyway, when they travel through the drift chamber, they knock some electrons off the atoms in the gas inside the chamber and those electrons (well, a cascade of electrons generated from the muon event) are accelerated to a wire strung in the centre of the chamber (the drift chamber is actually a particle accelerator and runs at about 10kV), where they are detected as an electrical pulse. By measuring the time between when the scintillators detected the event and when the signal reaches the wire in the drift chamber, we can figure out how far it was from the wire when it went through (5cm/us in the gas we're using). There's another trick that's used to get the position along the wire that the event comes in at (charge division, I can describe it if you ask), so the drift chamber actually gives an X-Y coordinate of the muon path through it. Because the drift chamber can't tell which side of the wire the event happened on, there are left and right scintillators and the information on which ones detected the particle are used to determine which side of the drift chamber it went through. Three more chambers are going to be added to the setup: one under the top one, and two more under the lead (the setup is obviously going to need to be changed when they're ready). Once that's done, we'll be able to create 3D images of the insides of objects we place in the middle of the system by using tomographic analysis of the paths of muons through the detector and object (like CT scans done in hospitals with x-rays)... just using cosmic rays that would already be passing through it normally (no new radiation is needed to take such a picture with this technique... it just takes a long time to do and so isn't workable for use on humans, in case you were wondering).
Some of my work. Developed in LabVIEW (my first LabVIEW project ever). The display in this picture is showing live data from a muon event... literally viewing the signature from a cosmic ray event (possibly originating from a supernova millions of years ago). The upper left signal is from the wire (the timing is used for the X direction), and the other four are from the charge division pads (that are used to determine the Y direction). The craggy graph at the top is just a count of how many events per second were detected (each event is stored in a file or sent over the network for analysis by another computer).
And, here's the drift chamber being tested in the clean room:
And that's how I spent my summer... ;).
The abstract that I submitted for the talk is:
It is becoming ever more important to monitor the flow of goods and people as a deterrent against state, criminal, or ideological organizations that may wish to wage war or cause serious disruption through the use of “asymmetric weapons” systems. While it can be argued that conventional weapons pose the greatest and most likely risk, and that nations need to protect against all forms of weapons smuggling, governments have a special obligation to prevent the use of chemical, biological, radiological, and nuclear (CBRN) weapons against their populations, infrastructure, services, and legitimate foreign interests. There are mitigation strategies that can be used to minimize the impact of a successful attack with chemical, biological, or radiological weapons; however, the damage that would be inflicted should a nuclear device be detonated in a populated area would be devastating beyond measure to both the fabric and spirit of any country, its operation, and its people. Radiation detectors, and active imaging with x-rays or gamma rays, provide a defence against unsophisticated smuggling attempts; however, these measures can be defeated through simple shielding or “cluttering” techniques. Passive Muon Tomography (PMT) systems are a technology that specifically addresses these limitations by being able to use the pervasive and weakly interacting, and thus highly penetrating, cosmic ray muon background to “look through” vehicles and containers. Statistical analysis of individual muon trajectories and momenta, as they undergo multiple Coulomb scattering in a heterogeneous target within a PMT system, allows the creation of a three dimensional tomographic map of the distribution of atomic nuclei within the target that can be used to detect the presence of high-Z nuclear materials or shielding that might mask the radioactive signatures of other, low-Z, materials of concern. Carleton University’s Physics Department is developing a proof-of-concept employing large drift chambers to determine that specific technology’s suitability and spacial resolution capabilities for use in PMT systems.I will need to do slides, but I'm pretty familiar with the material. I also have been thinking about revising the research paper I did in the winter term (3rd year honours research project in Integrated Sciences... done in my first year, ugh!) and submitting it to an undergraduate physics magazine for publication as an article (yes, there is a Canadian Undergraduate Physics Journal).
Here are a couple of pictures of the system as it stands (three more chambers are being built). This is a working cosmic ray telescope. What's interesting is that it's a project that would be within the abilities of a home hobbyist to design and build. I'm thinking about maybe trying to get the Physics Society at Carleton to start on a project to design and build a smaller system and then maybe publish the plans in Make magazine or something :).
This is the overall setup, with the telescope on the right, the scintillator electronics and high voltage (about 12kV) supplies in the middle, and the data acquisition system on the left (I was responsible for the scintillator electronics and the data acquisition system and programming):
This is a side view of the muon detector. It is a layer of scintillators on top, a “drift chamber” (it has the layers of blue foam that are visible from the side), another layer of scintillators right under the chamber (hard to see), a layer of lead (wrapped in brown paper), and another layer of scintillators near the floor. A particle or photon (e.g. x-ray or gamma ray) has to travel through all three scintillators before it's accepted as a valid “event”. The lead (about 6cm or so) blocks just about everything but muons, which don't interact with matter particularly much (they just bounce off the electron shells of atoms until they run out of speed and decay into electrons/positrons and neutrinos). Muons are produced when cosmic rays (ultra high speed protons and helium nuclei) smash into atoms in Earth's upper atmosphere. They only live around 2.2us, but survive the trip from the upper atmosphere to the ground because they are travelling at almost the speed of light and experience significant time dilation because of that (they only “see” the atmosphere as being a couple of thousand feet thick, and so it's not that far to them). Anyway, when they travel through the drift chamber, they knock some electrons off the atoms in the gas inside the chamber and those electrons (well, a cascade of electrons generated from the muon event) are accelerated to a wire strung in the centre of the chamber (the drift chamber is actually a particle accelerator and runs at about 10kV), where they are detected as an electrical pulse. By measuring the time between when the scintillators detected the event and when the signal reaches the wire in the drift chamber, we can figure out how far it was from the wire when it went through (5cm/us in the gas we're using). There's another trick that's used to get the position along the wire that the event comes in at (charge division, I can describe it if you ask), so the drift chamber actually gives an X-Y coordinate of the muon path through it. Because the drift chamber can't tell which side of the wire the event happened on, there are left and right scintillators and the information on which ones detected the particle are used to determine which side of the drift chamber it went through. Three more chambers are going to be added to the setup: one under the top one, and two more under the lead (the setup is obviously going to need to be changed when they're ready). Once that's done, we'll be able to create 3D images of the insides of objects we place in the middle of the system by using tomographic analysis of the paths of muons through the detector and object (like CT scans done in hospitals with x-rays)... just using cosmic rays that would already be passing through it normally (no new radiation is needed to take such a picture with this technique... it just takes a long time to do and so isn't workable for use on humans, in case you were wondering).
Some of my work. Developed in LabVIEW (my first LabVIEW project ever). The display in this picture is showing live data from a muon event... literally viewing the signature from a cosmic ray event (possibly originating from a supernova millions of years ago). The upper left signal is from the wire (the timing is used for the X direction), and the other four are from the charge division pads (that are used to determine the Y direction). The craggy graph at the top is just a count of how many events per second were detected (each event is stored in a file or sent over the network for analysis by another computer).
And, here's the drift chamber being tested in the clean room:
And that's how I spent my summer... ;).
