This is the "Geiger counter" I am currently using. Here is a brief review and some pictures. The
Eberline ASP-1 is a microcomputer based portable radiation measuring instrument.
Dual scales, lower scale indicates from 0-2500 volts (in 50-volt steps).
Upper scale represents radiation being measured. The meter scale is a simple 1.0 so there are no odd
or uneven scales to read. The meter also has a battery condition mark to indicate when the batteries
should be changed.
A nine position rotary switch is used to turn the unit on, check battery voltage, check the high
voltage,and select a range of operation.
The full-scale count is between approx 20 cpm and 3 million cpm, true count rate from the detector. It
has 6 multiplier scales of X100,X1K,X10K,X100K,and an unbelievable 1 million and 10 million scales
achieved through digital processing.
There is also a slow-fast-integrate response switch. In the fast position, the response time is selected
by the computer for typical survey work. When the slow position is selected, the response time is made
longer for a steadier reading. In the integrate position, the meter shows the total radiation detected
since the last time it was reset to zero.
This instrument also has dead time correction of none to 254 microseconds in 2 microsecond steps
typical dead time for gm is up to 100 microseconds depending on the probe and 2-10 microseconds
for scintillation probes as they recover faster.
Dead time compensation is a giant step forward in probe response and accuracy as the electronics
compensate for the probes slowness to recover from event to event.
High voltage output:
The high voltage can be set directly on the meter and ranges from 300-2,500 volts with no load and up
to +1600 volts with a 100 MOhm (or more) load.
This instrument also has adjustable threshold of 2-50 millivolts as well as gain adjustment that pretty
well eliminates any preamplifier unless the probe cable is extremely long.
MHV series coaxial
Input sensitivity is adjustable from 1mV to 50mV.
A speaker countdown circuit permits dividing the speaker rate by 16, 64, or 256 The speaker is
housed in an acoustic compression chamber that will accept typical headphones
Included are a few pictures, I borrowed a few as my cameras macro feature is horrible.
Once you start pumping voltages up over 15kv, you need to start worrying about
x-rays. X-rays will emanate out of the view port. Use a camera or a mirror, never look directly
into the view port. I use a video camera, with lead to block any stray rays.
Due to the thickness of my ss chamber walls, x-rays will not penetrate the walls
until we get over 40kv or so. At this point, I use lead shielding once again.
The Eberline ASP-1 is my choice to detect this type of radiation. I have included
a description and pictures of my unit below.
Warning: X-ray radiation is nasty stuff... it can cause burns and lead to cancer.
USE PROPER SAFETY EQUIPMENT!!!!!
Neutron radiation is even worse!
If you are pumping up the power above 40kv or so,
you need to worry about neutron radiation. Water, wax, and plastic
are all used to help block neutrons. Distance is always your best bet.
Neutron detection is another ball game. These are quite a
bit harder to find then geiger counters, and quite more expensive.
Gas proportional detectors such a BF3 and He3 work well, the better being
the He3. Scintillator detectors are quite a bit cheaper, but not nearly as good.
The bubble detector is relatively new, and cheap.
It is what I am currently using. Below is a link to them.