I did a thing

Today, I successfully defended my PhD dissertation! Now I am Almost PhD!

Now and then
Then (Jan 9 2019) and now (Nov 12 2020)

The only thing left to do now is make sure the requisite paperwork gets all the signatures and turned in to the Graduate School, and to finish up writing the dissertation. The dissertation is pretty much completed now. Just a few more modifications to make and I’ll have another draft to send to my advisor for feedback. I’ve got about three weeks before the submission deadline, but hope to have it ready to submit before that. Then the final step will be the graduation ceremony in mid-December.

Inside some Radcal Accu-kV sensors

The kV sensors in one of my Radcal 9000 kits failed calibration, and unfortunately Radcal no longer has spare detector modules available to rebuild the sensors anymore, so I had them just recalibrate the ion chambers and send everything back.

I use the Radcal kits primarily for making fluoroscopy exposure measurements and the Accu-kV meter and kV sensors don’t really get much use these days. I have other meters that I used for x-ray tube voltage and exposure measurements, so losing the Accu-kV sensors isn’t a big deal.

Since I’m taking them out of service anyway, I thought I’d crack the sensors open to see what’s in them. I only had to undo a few screws to get the cover off

Under the cover is a stepped copper filter that attenuates the x-ray beam by different amounts. The ratio of attenuation through the different filter thicknesses is used to calculate the x-ray tube voltage. The filters are attached to a block of lead that blocks x-rays from getting to the rest of the sensor. A little bit of wiggling and gentle prying let me lift the block out to look at the insides.

The sensor module itself fits snugly into the lead block and is held in place by a brass bar screwed into the lead. The circuit boards contain a couple of AD822 op amps and supporting components that take the signal from the sensor module and send it to the 4082 meter.

kV sensor module
kV sensor module

The kV sensor module itself appears unremarkable. There’s a white plastic 4 x 6 x 40 mm bar glued to the black carrier board. I have a vague memory of the 40×5 kV sensors being photodiode type detectors, so the white plastic would probably be some kind of scintillator material, and there would be some photodiodes underneath. Not positive about that though, so I’ll have to do a bit of digging to find out.

The 40×5-MO mammography kV sensor is similarly constructed, and aside from having to undo a few more screws, came apart pretty easily.

The sensor module in the mammography sensor fits into a brass block, and the stepped filters are much thinner (possibly aluminum?). The sensor module itself is virtually identical to its 40×5-W counterpart.

When I get some spare time, I’ll get some x-ray images of the sensor modules to see what’s in them. Then I’ll put them back together and they’ll become part of my museum collection.

Update: Here’s an x-ray image of the detector modules. The row of pin headers is in the middle, and the square blocks are the individual detectors.

X-ray of the 40x5-W and 40x5-MO detector modules
X-ray of the 40×5-W and 40×5-MO detector modules

Spotting NEOWISE

Got out the last couple of evenings to get some photos of Comet NEOWISE before it goes away for the next ~6700 years.

The comet itself was pretty easy to spot. After about 9PM EDT, the sky was dark enough for me to see the brighter stars. Found the Big Dipper and looked down toward the horizon. I wasn’t able to see it with the naked eye where I was (too much light pollution), but it was pretty easy to capture with my camera using a 5s exposure.

Captured these (out of a bunch) with my 18-55 mm lens using a 5s exposure at 1600 ISO. My camera is pretty noisy at high ISO and there are a few artifacts, but the big dipper and the comet are pretty easy to see.

The next evening I went back out with my 18-200 mm lens to get a few more shots. Stayed with a 5s exposure and went with 800 ISO to reduce the noise a bit. These shots turned out a little better.

Zooming in at 200 mm gives a nice image of the comet and its tail.

Have a bunch of images that I took that I need to stack together, which should make for some pretty nice images. That will have to wait until later when I have more time.

First colonoscopy

Apparently, turning 50 activates several medical milestones.

My doctor says the colonoscopy is a rite of “passage”.

Yesterday was the prep for the colonoscopy. Everybody will tell you the prep is the worst part.

They’re all correct.

No food, only clear liquids for the whole day. Then it begins. The solution that cleans out your insides. Mine was a 4 liter jug of Gavilyte that I mixed up in the morning and let chill in the fridge. Pro tip: Before mixing, check to make sure the jug has no damage, holes, or cuts. I had filled mine half way and started shaking to mix it when stuff started leaking out. Found a cut near the handle, possibly from someone cutting too deep when unboxing.

The solution is not the most pleasant to drink, even with the included flavour packet (mine was lemon). Slightly viscous, tastes plasticky, and just down right icky. Some reviews I saw at WebMD suggested holding your nose and drinking through a straw to avoid the taste. Wish I had seen that before I started drinking.

I was only able to make it through just under half of the 4 liters of prep solution before I got to the point where it was going to start going out the way it came in. Seemed counterproductive to try to keep going at that point. The rest of the evening and night was spent sitting up in bed trying not to throw up, and napping in between trips to the bathroom. Fortunately, what I was able to get down was enough to clean out my innards well enough to go forward with the colonoscopy today.

Colonoscopy day was pretty uneventful by comparison. Arrived at the hospital, checked in, and waited a bit before they brought me back to get ready for the procedure. Then I got wheeled in to the procedure room. Closed my eyes to rest a bit while everybody was getting things ready, and then next thing I know I’m waking up and back in the bay I started in.

After about 15 minutes of waking up enough to stand and get dressed again, I was wheeled out to the main entrance where Connie was waiting with the car and two Wendy’s spicy chicken sandwiches for the drive home. After practically no food for almost two days, the chicken sandwiches really hit the spot.

Got a clean bill of colonic health, so now I don’t have to do this again for another 10 years.

Note to self: Think about adjusting my diet a few days prior to the next colonoscopy so that there’s less “stuff” left to clean out of me. That might make the prep easier.