The table below gives estimates of effective area based on a criteria
of >3 photons in detector, all with energy>10KeV. Effective
areas are in m^2-sr. The effect of atmospheric attenuation of
photons, and response of BGO is included. Lynn Lake mag
fields are assumed. The assumed detector is 2x2 m x 1 cm
BGO. We fit the effective area vs energy points to a quadratic in
energy, and convolve these with the diffferential electon flux, based on
our ApJ parameterization dn/dE = 227 E^-3.09. The 3nd column is the
number of events in a 100 day flight for the detector above.
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Variation of Aeff with longitude for southern polar orbit.
The plot below show Aeff @ 2Tev, vs longitude
for latitude 70S. The variation in Aeff over and orbit is about a
factor of
two peak to peak. It turns out (by accident)
that Lynn Lake (the location I was running previously) is not too far from
the average.
The variation of Aeff with longitude is a weak
function of electron energy, with a smaller variation at higher energy.
Below is a plot of the detected distribution of mean photon energies,
for primary power laws of -3,-3.5, and -4. The
same total electron flux >1 TeV is assumed in each case. The
number of observed events is a factor of 3.5 smaller
for a spectral index of -4 compared with -3, assuming identical true
integral flux.
Taking as a simple measure of the ability to measure the primary spectral
index the ratio of events with mean photon
energies > 250 KeV to the total number of events....
for a spectral index of -3, this ratio is 0.58 +/- 0.05
for a spectral index of -4 this ratio is 0.27 +/- 0.06
Below is a scatter plot of the x vs y direction cosines of observed
events. Inclined incident angles are favored.
Finally, here is a plots of the distribution of zenith angles for the observed events.
Here is the distribution of photon production altitidudes (in cm) in
observed events. Balloon altitude is assumed to be 36 km. Roughly
half of the photons are generated within 10 km of the instrument.
Here is the distribution of the number of photons seen in an event.
The trigger threshold is set at 4.
