Computed parameters for 12 m focal length Laue telescope optimized for observations of GC 511 keV source.
Cu and Ag crystals of 0.5 arcminute mosaic width are assumed everywhere. The four lowest reflection types 
(111, 200, 220 and 113) are used in separate rings. The Cu and Ag rings partly overlap and therfore cannot
deliver the full diffraction efficiency as computed here, a 20% loss in overall efficiency must be expected.
(Other reflection types are shown for illustration only). A 3x3cm2 detector is assumed, the individual
Laue crystals are also assumed to be 3x3 cm2, but some rings are too close to accomodate this size crystals.
The resulting efficiency loss must be evaluated later, but will not exceed 10%.

In summary: Assuming that we can get the proper crystals (and learn to cut them into shape without destroying the 
crystal structure!) we should be able to achieve an effective area in excess of 500 cm2 at 512 keV feeding the 
9 cm2 detector.

NOTE: The calculation assumes a point source! For an extended source only the flux from (about) the central 10 
square arcminutes will be collected. This is a major risk! - if the central GC point-source is extended across a 
degree we may not get a significant result - even if the telescope works as theoretically predicted in every respet! 
The full evaluation of the response of the telescope to an extended source is an important job TBD! 

Reflection     Bragg   Ring    No of      Cell    Thickness Crystal Diffraction Collection Integrated Integrated
  type      Z  angle  radius crystals  FormFactor thickness   mass   efficiency    area       area    x-tal mass
              (arcmin) (cm)   in ring (electrons)   (mm)      (kg)      (%)        (cm2)      (cm2)     (kg)

 Cu(111)   29   20.0   14.0     28        88.3      4.2       0.9       31         75.6        75.6      0.9
 Cu(200)   29   23.1   16.1     33        82.8      4.6       1.1       30         84.6       160.2      2.0
 Cu(220)   29   32.7   22.8     46        67.1      5.7       2.0       25        101.0       261.2      4.0
 Cu(113)   29   40.0   27.9     57        56.9      6.4       2.8       22        111.0       371.2      6.8
 Cu(222)   29   38.3   26.7     55        59.1      6.3       2.6       23        110.2
 Cu(133)   29   50.3   35.1     72        45.8      7.4       4.1       19        117.6

 Ag(111)   47   17.7   12.4     25       149.7      2.9       0.7       33         70.8       442.0      7.5
 Ag(200)   47   20.4   14.3     29       141.9      3.2       0.8       31         78.3       520.3      8.3
 Ag(220)   47   28.9   20.2     41       120.3      4.0       1.5       27         95.7       616.0      9.8
 Ag(113)   47   35.4   24.7     50       107.0      4.6       2.1       24        104.2       720.2     11.9
 Ag(222)   47   33.9   23.7     48       109.8      4.5       1.9       25        102.7
 Ag(133)   47   44.5   31.1     64        92.8      5.4       3.1       20        112.6

 Au(111)   79   17.7   12.4     25       264.8      1.0       0.4       33         71.8

 Pb(111)   82   14.6   10.2     21       286.1      2.0       0.4       30         53.7