Cosmic Rays, mounting angle, pancake detector

  • Sonarflash
  • Sonarflash's Avatar Topic Author
  • Offline
  • Premium Member
  • Premium Member
  • Blind since 1966 - 51+ years with insight.
More
8 years 8 months ago #1518 by Sonarflash
Greetings with a curiosity
The past month, I've had my Aware RM-80 (LND7313 pancake) detector lying flat on the sill, window open. So, the 44mm diameter mica window has been facing up.
Counts have averaged 30 cpm, as high as 33 cpm.

24 hours ago, with the rainy, windy weather much the same for the past four days, I placed the detector on edge, the mica window facing south, into the window screen. There is a fairly steady light, chill draft coming into my room.
Average reading for the past 24 hours dropped sharply to 26 cpm with the 1sigma Standard Deviation dropping from near 6 to 5.2.

Question is, has anybody else with a pancake detector noticed a similar count differential when changing from horizontal to vertical?
My thought is that the narrow edgewise profile and very robust, thick stainless steel sidewall of the LND pancake tube causes this change.

To confuse this issue, a friend in Ontario bought a Masur GC last year (also a 44mm pancake). He tried this and didn't notice any count differential between the unit standing vertical or sitting horizontal. In that case, I don't know how long he collected data.
Sonarflash, VA7BDG

Please Log in or Create an account to join the conversation.

  • Sonarflash
  • Sonarflash's Avatar Topic Author
  • Offline
  • Premium Member
  • Premium Member
  • Blind since 1966 - 51+ years with insight.
More
8 years 8 months ago #1563 by Sonarflash
Well, my readings are back up around 30 to 33 CPM. I put the detector flat, mica window up and background jumped back to the high readings. When the mica window is facing south, the detector on edge, it was averaging around 24 to 25 CPM.

Makes sense that with more surface area pointing at the sky, the readings should be higher. Especially since the LND7313 tube has a narrow side profile and thick stainless steel sidewall. I'm going to test this with my little LND712 end-window probe on the GK+4 counter.
One Google site referring to cosmic ray detection mentioned mounting the detector at a 30 degree angle facing south, which originally got me interested in testing detection angles.

Please Log in or Create an account to join the conversation.

More
8 years 8 months ago #1571 by Juzzie
It would be interesting to see what happens if you face the mica window down, though that may introduce other variables like wood (K40?) or stone (uranium/thorium and/or friends). I can't imagine cosmic rads being stopped by the stainless wall of the lnd pancake, and likewise that there should be so much difference in cosmic influence by the sideways orientation of the gm tube.
Radon progeny like to attach to dust and particles in the air then settle. There is a constant "rain" of radon progeny, to varying degrees, and this may affect an upward facing pancake....or, I guess, a downward facing one...
I might experiment with an LND 7317 :)

Owner and operator of "southofhobart" monitoring stations.

Please Log in or Create an account to join the conversation.

  • Sonarflash
  • Sonarflash's Avatar Topic Author
  • Offline
  • Premium Member
  • Premium Member
  • Blind since 1966 - 51+ years with insight.
More
8 years 8 months ago #1573 by Sonarflash
Hello Down Under.
I did try the pancake upside down, horizontal, spaced away from any surfaces. The readings were higher that way than when the detector was vertical. I'm pretty sure it has more to do with the GM tube profile. A lot smaller surface area being being exposed to space. You're probably right about the thickness of the SS back and sides.

Another thing I did before joining Radmon was to enclose the RM-80 detector in a zippered nylon camera bag to prevent dust settling on the mica window or mesh window.
I blow off the mica window. A careful blast of compressed nitrogen is recommended. The SS mesh window fitting can unscrew, so I've regularly scrubbed the mesh clean ... especially after dragging the detector through a few local mine shafts.

Radon levels are very low in the Cowichan Valley. Dryer lint shows some fast decay progeny, but a fresh batch in my son's house would average 60 to 70 cpm, then readings would quickly fade to under 30. In this apartment last year, I used a vacuum cleaner and coffee filter and down off the floor, got over 120 cpm that also quickly decayed to background. That's why I keep my window open a little and the detector sits in the draft.
I'll rig a stand and mount it upside down, plus put it in a zip-lock baggie later today, then we can watch the station levels.
Sonarflash, This email address is being protected from spambots. You need JavaScript enabled to view it.

By the by, I'm an avid rockhound. Got any spare minerals? I collect thumbnail sized specimens.
Brian

Please Log in or Create an account to join the conversation.

  • Sonarflash
  • Sonarflash's Avatar Topic Author
  • Offline
  • Premium Member
  • Premium Member
  • Blind since 1966 - 51+ years with insight.
More
8 years 8 months ago #1574 by Sonarflash
Here's an addendum.
The RM-80 detector is now air cleansed, screen washed and enclosed in a freezer zip-lock baggie. I'v mounted it mica window facing down, 10" above the window ledge, still catching a breeze.
New readings started 07:50 PST.
Tomorrow at the same time, I'll flip it over, mica window facing up, still in the baggie, still 10" above the window ledge.
We shall see...

Please Log in or Create an account to join the conversation.

  • Sonarflash
  • Sonarflash's Avatar Topic Author
  • Offline
  • Premium Member
  • Premium Member
  • Blind since 1966 - 51+ years with insight.
More
8 years 8 months ago #1578 by Sonarflash
Okay Folks,
A bit early, I've flipped the RM-80 detector around, face up, still in the plastic baggie, still on mounting ten inches above window ledge, still in draft. Wiped the plastic clean.
Average cpm over the past 24 hours was 31. Not much difference.
In 24 hours, will mount the detector sideways, as above, narrow edge towards space, mica facing south (metal window screening).

Did this a bit early as I have a ham club breakfast to attend in half an hour...
Regards

Please Log in or Create an account to join the conversation.

Moderators: Gamma-Man
Time to create page: 0.207 seconds
Powered by Kunena Forum
Everything's free. Please support us by considering a donation. Log in first!
Solar powered Raspberry Pi 4 server stats: CPU 26% Memory 13% Swap 15% CPU temp=61.8'C Uptime 34 Days