# Rate Estimates

## Previous experiment at the IAC   IAC apparatus for positron production experiment Counts observed when the dipole is tuned to direct positrons onto the Ta target Counts from electrons on Ta target
HpGe observed about 1 annihilation photon per 10 microCoulombs of electrons on the upstream Tungsten target
Ratio of annihilation photons observed when using positrons to electrons 120 to 10
Bend 2 Dipole Spot size at 2nd Dipole D2 Spot size at Phosphorous Target
 Condition Grade Calculation Electron Beam Energy 10 MeV Peak current 40 mA Pulse width 100 ns Rep Rate 300 Hz

## NaI rate Ratio of positron to electron beam

### Assumed Geometry

Assume a 2 mm thick Tungsten target that is 1" square

The target is located at -80 < Z < -80.2

The NaI crystal is 2.32" or 56.49 mm in diameter

The NaI crystal is 8" from the target then the opening angle is atan(2.32/8/2) = 8.25 degrees

### Chromox target

Chromox target is 0.011" thick = 0.279 mm

#### G4 Chromox description

G4Element* Cr =
new G4Element("Chromium", "Cr",z=24., a= 51.9961*g/mole);

G4Element* Al =
new G4Element("Aluminum","Al", z=13., a= 26.98154*g/mole);

//
// typically the viewers are 99.5% Al_2 O_3 and 0.5% Cr_2 O_3
//
// I will construct a material that is 99.5% made of  2 Al and 3 O  Atoms/nuclei
//             and 0.5% made of  2 Cr and 3 O  Atoms/nuclei
//
//   Al = 99.5 * 2/5 = 39.8 %
//  O = 99.5 * 3/5 = 59.7 %
//  O = 0.5 * 3/5 = 0.3 %
//  Cr = 0.5 * 2/5 = 0.2%
//
// Jlab PePPo Chromox viewer is 0.011" thick = 0.279 mm
//
//

G4Material* ChroMox = new G4Material("ChroMox", density= 3.85*g/cm3, nel=3);



## Rates using GEANT4

Assume 3 MeV electron and positron beam.

### 2 mm Thick Tungsten annihilation target

Integrating between 0.3 and 0.7 MeV (511 peak unclear)

Integrating between 0.5 and 0.53 MeV