Spring 1996 Issue

Questions and Answers

All questions with their answers for the spring '96 issue will be posted on this page.

El-Mul Technologies Ltd.,
"The Micro Sphere Plate: a novel electron multiplier"

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."

Question from James White, Texas A&M Universtiy (jtwhite@d0tam2.tamu.edu)
"You show the ``relative'' sensitivity for electrons, but in none of the papers we've found is the absolute efficiency discussed. Is this known yet?"

Answer from El-Mul
"Electron detection efficiency is, typically, 50-75% for electrons of 0.5-4 KeV and under 50% for other electrons."

Last modified: 17 Oct 1997, Jochen.