Ultimately, the concept of a crystal diffraction telescope should be put to use in space where longer exposures and steady pointing will result in outstanding sensitivities. MAX (artists view), a space borne crystal diffraction telescope  using a gamma-ray lens will consist of a tunable crystal diffraction lens (see : the prototype tunable lens) situated on a stabilized spacecraft, focusing gamma-rays onto a small array of germanium detectors perched on an extendible boom (6-19 m).
In order to take maximum advantage of the particular properties of a focused gamma ray beam, a germanium detector matrix will be used similar to the one used for our balloon telescope CLAIRE consists of 3x5 detector elements, each one with a geometric surface of 3x3 cm and a height of 7-8 cm. The 2.8 cm FWHM focal spot produced by the lens will optimally be pointed at one of the central detector elements. Using isotopically enriched 70Ge as detector material will reduce the b- background component in the energy range of the lens while the enhanced b+ production only effects the background above 1.5 MeV. Further reduction of the non-localized nb components will be possible using the 15 matrix segments. The matrix also offers the possibility to monitor the remaining background simultaneously to the astrophysical observation. Since the spacecraft is seen under a small solid angle, a low intensity of cosmic-ray induced background is anticipated, this will allow us to use a detector shielded only by a very light anticoincidence shield.
Since the focal length of the lens is increasing with energy, a retractable boom (i.e.. a coilable tube mast) will be used to vary the distance between spacecraft and detector along the optical axis of the lens. Booms have been used in gamma-ray astronomy on Apollo 15 with a NaI detector and on Mars-Observer for the Ge detectors. In both cases, the extension was around 7 m.

Deploying the detector on a boom instead of the diffraction lens has several striking advantages: The mechanical requirements on the mast rigidity are less severe since a Germanium detector array is small and lightweight and thus easy to handle on a boom; moreover, twists and bends of even up to a few cm’s are tolerable, as the focal spot (ø 2.8 cm) can wander around on the detector array (total surface 9x15cm) without significant loss of sensitivity. On the other hand, the stringent requirements for the pointing of the lens (typically ~ 5”) can be satisfied on board the pointed and stabilized spacecraft. Finally, moving the detector away from the spacecraft reduces the background by up to an order of magnitude. In order to have a mechanically redundant system, the spacecraft will feature two ‘detector-boom systems’. If both detectors were to be operated at the same time, different energy-bands could be observed simultaneously, or, maximum sensitivity at one energy band can be achieved by combining the two collector-zones.

The sensitivity calculations shown below assume a lens configuration with 544 Ge crystals, mostly with a 2 * 2 cm^2  surface, and a total lens area of 2676 cm^2. The mosaic width is assumed to be 10 arc seconds, and the crystals are 1.5 cm thick. The focal length would be 16.6 m at 511 keV, increasing linearly with energy. The calculations assume a detector made up of 70Ge-enriched HPGe elements with a 3*2 cm^2 surface and length of 7 cm. The detector efficiency was assumed to be 80 % at 200 keV, 54 % at 511 keV, and 39  at 1000 keV. The background was estimated using a fit to the GRIS continuum background spectrum for a 70Ge-enriched HPGe detector during a balloon flight in Alice Springs in 1992. The background was reduced by a factor of five to roughly account for the lower mass of the anticoincidence shield needed, which reduces the contribution of secondary particles. This gives a background estimate of $9.42 \cdot 10^{-4} \left( \frac{E}{100keV} \right)^{-1.054}$ counts cm$^{-3}$ s$^{-1}$ keV$^{-1}$. This is of course a very crude estimate and emphasizes the need for detailed Monte Carlo background simulations.