Question from David L. Knies (Knies@nrlfs1.nrl.navy.mil)
"How would the MSP detection system respond to 12 MeV heavy ions?
We have need of a position sensitive detector for
heavy ions in the mass range of (H-U).
The detector would also have to be rad hard."
Answer from El-Mul
"The direct efficiency of MSP, like MCP(microchannel plate), is very
low at that energy. To get a good efficiensy, the recommended
configuration is to place a thin foil above the MSP, coated with a
special material. MeV Ions hitting this foil on one side cause an
emission of few electrons from the other side of the foil.
These electrons are then accelerated towards the MSP (by 500 V),
where they can be efficiently detected.
In order to get position sensitivity, one has to use a phosphor
screen with the MSP or MCP.
The resolution is of the order of 1 mm when the foil technique is used.
After accumulated output charge of about 0.01 C/cm^2, the MSP gain
drops to half of its initial value.
At a gain of 10^6 this corresponds to input charge of 10^-8C/cm^2,
which is 10^11 ions or electrons / cm^2.
Incrementing the voltage by 100V will bring the gain back to
its original value."
Answer from El-Mul
"Electron detection efficiency is, typically, 50-75% for electrons
of 0.5-4 KeV and under 50% for other electrons."