Radiation of photons in process of charge particle volume reflection in bent single crystal

New type of radiation in crystals is predicted and investigated in computer simulation. It is shown that process of volume reflection of electrons and positrons in bent crystals is accomplished with high-power radiation of photons. Volume reflection radiation has intensity comparable with known channeling radiation, but it is less sensitive to entrance angle and sign of charge of a particle. Simulated spectra of radiation power are presented for 10 GeV and 200GeV particles.Comment: Latex, 8 pages, 4 fig

A perspective on biological x-ray and electron microscopy

Abstract. We consider image contrast for electron microscopy of thick hydrated biological specimens, allowing for the use of phase contrast and energy filtering. This allows us to gain perspective on the relative roles of electron and soft X-ray microscopes. Radiation dose is found to depend strongly on ice thickness, with electrons offering lower dose if the ice thickness is less than about 500 nm, and x rays offering lower dose for thicker ice layers

Measurement of pair-production by high energy photons in an aligned tungsten crystal

A new measurement has been made of the rate of pair production in a 3.2 mm thick tungsten crystal, exposed to photons with energies in the range 10 to 150 GeV, for angles of incidence up to 10 mrad from the crystal axis. A strong enhancement of the pair-production rate is observed when the beam is aligned along the crystal axis, as compared to a random orientation. This effect can be exploited in the NA48 CP- violation experiment by using a thin crystal rather than an amorphous material to convert photons, thus minimising the scattering of kaons in the converter

Antiproton stopping power in hydrogen below 120 keV and the Barkas effect

The simultaneous measurement of the spatial coordinates and times of p¯s annihilating at rest in a H2 target at very low density ρ (ρ/ρ0<10-2, ρ0 being the STP density) gives the possibility of evaluating the behavior of the p¯ stopping power in H2 at low energies (below 120 keV). It is different from that of protons (the Barkas effect). Moreover, it is shown that a rise at low-energy values (≲1 keV) is needed to agree with experimental data