A positron source using an axially oriented crystal associated to a granular amorphous converter

Abstract

A non-conventional positron source using the intense γ radiation from an axially oriented monocrystal which materializes into e+e− pairs in a granular amorphous converter is described. The enhancement of photon radiation by multi-GeV electrons crossing a tungsten crystal along its <111> axis is reported. The resulting enhancement of pair production in an amorphous converter placed 2 meters downstream, is also reported. Sweeping off the charged particles from the crystal by a bending magnet upstream of the converter allows a significant reduction of the deposited energy density. Substituting a granular target made of small spheres for the usual compact one, makes the energy dissipation easier. The deposited energy and corresponding heating are analyzed and solutions for cooling are proposed. The configurations studied here for this kind of positron source allow its consideration for unpolarized positrons for the ILC.

Positron sources: from conventional to advanced accelerator concepts-based colliders

“…In this approach, a bending magnet can be installed between the radiator and the target-converter, which allows sweeping off the charged particles emerging from the crystal (Chehab-Strakhovenko-Variola scheme), hence reducing the thermal and radiation load being of great importance for the linear collider projects. Moreover, a new option of the target-converter can be also considered implying the use of a granular target made of small spheres providing better heat dissipation and better resistance to thermal shocks [99]. The hybrid scheme, thus, has been adopted by CLIC as a baseline for the unpolarized positron source.…”

Positrons sources and related activities for Future Linear Collider at LAL Orsay Laboratory

“…For the latter the Peak Energy Deposition Density (PEDD) is a critical parameter. In [6] the authors, using the experience of the target for muon collider, shown that using a granular target instead of compact reduces the PEDD (Table 2). The high ratio of surface volume of the spheres (3/r) makes easier the thermal dissipation.…”

Silicon crystals for steering high-intensity particle beams at ultrahigh-energy accelerators

“…Crystal-based solutions [47] are also under consideration for the slow extraction of circulating beams in the Super Proton Synchrotron (SPS) at CERN [48] or at synchrotron facilities [49]. Aside from particle beam steering, crystals could also be used as innovative elements for generation of hard radiation [50,51] or positron [52] beams and for the realization of compact photo-converter [8] and forward electromagnetic calorimeters [53,54].…”

“…As compared to traditional magnetic optical elements used in accelerators, crystals operate without the need of a power source, generally do not require a cryogenic environment, and are extremely compact and light-weight, typically less than 1 Kg, making them appealing for integration in particle accelerators. The use of crystals have been suggested also for the Future Circular Collider (FCC) [39,41,[55][56][57], the International Linear Collider (ILC) [52,58], the Compact Linear Collider (CLIC) [58,59], and the Circular Electron Positron Collider (CEPC) [60] and it could be exploited in a future muon collider design [61,62]. Given the extremely high intensity and energy reached in modern and future particle accelerators such as the HL-LHC or in future planned ones, the implementation of bent crystals at these facilities demands facing various technological challenges and a considerable improvement of the state-of-the-art in the manufacturing of crystals for scientific or technological application.…”