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.

Life in the time of COVID-19

Life for a lot of people has changed pretty drastically over the past few weeks as the COVID-19 virus takes hold in the US. Several states have enacted “Stay home” emergency directives, while others like South Carolina are trusting its residents to maintain social distancing. Based on what I’ve seen on the news and the few times I’ve had to venture out to shop, that seems overly optimistic.

A few weeks ago, my wife had us start monitoring our body temperatures twice a day, which seemed like a good idea. Then a few days later work issued a mandatory requirement for all employees and students to start self-monitoring for COVID-19 symptoms. Monitoring for symptoms at least gives people a window of time to figure out where and when they might have been exposed. I’m lucky to have a wife who’s so proactive and stays on top of things like this.

On my end of things work has encouraged anybody who can work from home to do so. Although the majority of my work can’t be done from home, I took advantage of being able to work from home to get caught up on writing up reports that should have been done a few months ago, but got put on the back burner so that I could get caught up on the equipment testing. Now that I’m finally caught up on the reports, I can move on to start getting caught up on other things like the mandatory annual training modules and earning more continuing education credits (didn’t get many last year because of being so busy and I’m starting to run low).

After discussing the equipment testing situation with my colleagues at work, I also decided to temporarily suspend the regular equipment testing to reduce the chance of me transporting COVID-19 around work and also to reduce my risk of exposure. It will mean scrambling to get caught up later when things start getting back to normal (whenever that ends up being), but I felt it was a prudent thing to do.

With a reduced work workload and working more from home, I now have the opportunity to spend more time on my PhD work. With the majority of my Monte Carlo simulations completed, I’ve been going through the data and doing some analysis on it. Now I can spend more time doing that and start writing up my results. I have until September or October to cobble my thesis together, and that time will no doubt go more quickly than I want.

Song obsessions

Every now and then my brain gets fixated on a particular song at a level that goes way beyond ear worm. It gets embedded in there and my brain keeps stirring it up the way one might absent-mindedly fidget with a pen, or twiddle a lock of hair.

The latest one is Sound of Silence by Simon and Garfunkel, probably partly triggered by my post-DST tweet.

It’s been on a pretty much non-stop loop in my brain all week.

Fortunately it’s a song I don’t mind and it hasn’t driven me crazy yet.

While listening to the Simon and Garfunkel version on Youtube, I came across this pretty awesome cover version by the heavy metal group, Disturbed.

One possible reason my wife offers for the continued looping in my brain is that since Sound of Silence doesn’t really have a firm definite ending, my brain keeps replaying it trying to end it. Seems plausible.

At some point, probably in a few more days or so, the song will fade and my brain will find something else to fixate on. In the meantime, here’s another cover version by Pentatonix.