Vacuum cleaner shopping

Well, the epoxy job I did on my old Dyson vacuum cleaner didn’t last quite as long as I thought it would.

Broken Dyson
Broken Dyson

Maybe I didn’t use enough epoxy, although I think if I made the epoxy layer much thicker, things like the hose and bin wouldn’t have snapped back into place as easily.

I think rather than trying to slather on more epoxy, it’s time to retire this Dyson. It’s done an excellent job over the past 10 years. Mostly likely it will be replaced with a Dyson Animal Ball 2, which has only a slightly smaller bin capacity than my DC15 (2.0 liter vs 2.5 liter for the DC15), and significantly larger bin than the other newer model Dysons that I’ve seen.

Dyson tear down to come.

Manual kmod rebuild

Just leaving a note to myself for future reference.

Needed to rebuild the kmod-wl package because of a borked update process (something made the computer crash mid-update).

A bit of Google searching brought me to the script in /etc/kernel/postinst.d/akmodsposttrans.

Running sudo /usr/sbin/akmods --from-kernel-posttrans --kernels `uname -r` rebuilt the missing kmods and a modprobe wl got the wifi back up and running.

Summer reading pile

My pile of reading for the summer.

Summer reading
Stacks of Radiology and Radiographics

One of the radiologists leaving the department set out his collection of journals (Radiology and Radiographics) for anyone to grab, presumably because he didn’t want to move them (I wouldn’t want to either).

I decided to grab them because I figured they’d be interesting to flip through, and it’s always good for diagnostic medical physicists to know what’s going on with the clinical side of things.

Even though I can look at all the articles in these journals online, I find sitting down with a journal and flipping through it so much more satisfying.

It’s unlikely I’ll keep all of them. I’ll spend some of my evenings going through two or three issues at a time and keep the ones with interesting articles for later reference.

No more Radio Shacks

The last Radio Shack in the Charleston area is closing (well technically there is one more, but it’s a franchise store and I have no idea if it’s going to keep the Radio Shack name).

I happened to be in the area and stopped by to check and saw the signs. Not sure when their final day is, but judging from how picked over their inventory was, I’d guess it’s pretty soon.

All their component bin inventory was hanging up on the shelves, and was listed for $1/package. Not quite as good a deal as the $0.15/package I got when the Radio Shack near me closed out. Most of the other inventory was listed at 70-90% off.

There wasn’t much left in the store, but I did find a few things that I thought was a good deal at $1/package. Picked up the rest of the SMA edge connectors and DPDT mini toggle switches. Also picked up a heat sink and a few BNC barrel and T adapters for 90% off. The batteries were marked down a fair bit and at 2 for 1 also, so I picked up a few N cells to use in my HP 28S.

Final Radio Shack haul
Final Radio Shack haul

Focal spot blooming demonstration

Continuing on with my experiments with my pinhole grid, here’s a demonstration of focal spot blooming.

In a typical x-ray tube, you have electrons being emitted from the cathode filament and accelerated toward the tungsten anode. Being all the same charge, the electrons in this beam will naturally repel each other causing the beam to expand slightly before hitting the anode. When the tube current is low, there aren’t many electrons in the beam, so not a lot of expanding occurs before the anode is reached.

At high tube current, you have a lot of electrons coming off the cathode and going into the beam. Lots of electrons in the beam means more repulsion and you get much more expansion of the beam by the time it reaches the anode as a result.

Here’s an image I acquired using my pinhole grid at 50 kV, 50 mA and 100 ms (5 mAs). 50 mA is a pretty low tube current and about as low as most machines will go.

Focal spot blooming
Demonstration of focal spot blooming at low tube current. Acquired at 50 kV, 50 mA, 100 ms, 181 cm SID

Now here’s an image acquired at 50 kV, 500 mA and 10 ms (5 mA).

Focal spot blooming
Demonstration of focal spot blooming at high tube current. Acquired at 50 kV, 500 mA, 10 ms, 181 cm SID

Note  how much larger the focal spot images are at high tube current. This is focal spot blooming, and can result in an increase in focal spot size by up to a factor of 2 depending on the tube current.