Abstract
The CERN-NA-59 experiment examined a wide range of electromagnetic processes for multi-GeV electrons and
photons interacting with oriented single crystals. The various types of crystals and their orientations were used for producing
photon beams and for converting and measuring their polarisation.
The radiation emitted by 178 GeV unpolarised electrons incident on a 1.5 cm thick Si crystal oriented in the Coherent
Bremsstrahlung (CB) and the String-of-Strings (SOS) modes was used to obtain multi-GeV linearly polarised photon
beams.
A new crystal polarimetry technique was established for measuring the linear polarisation of the photon beam. The
polarimeter is based on the dependence of the coherent pair production (CPP) cross section in oriented single crystals
on the direction of the photon polarisation with respect to the crystal plane. Both a 1 mm thick single crystal of Germanium
and a 4 mm thick multi-tile set of synthetic Diamond crystals were used as analyzers of the linear polarisation.
A birefringence phenomenon, the conversion of the linear polarisation of the photon beam into circular polarisation,
was observed. This was achieved by letting the linearly polarised photon beam pass through a 10 cm thick Silicon single
crystal that acted as a ‘‘quarter wave plate’’ (QWP) as suggested by Cabibbo et al.
2005 Elsevier B.V. All rights reserved.
PACS: 29.27.Hj; 41.60.m; 42.81.Gs
photons interacting with oriented single crystals. The various types of crystals and their orientations were used for producing
photon beams and for converting and measuring their polarisation.
The radiation emitted by 178 GeV unpolarised electrons incident on a 1.5 cm thick Si crystal oriented in the Coherent
Bremsstrahlung (CB) and the String-of-Strings (SOS) modes was used to obtain multi-GeV linearly polarised photon
beams.
A new crystal polarimetry technique was established for measuring the linear polarisation of the photon beam. The
polarimeter is based on the dependence of the coherent pair production (CPP) cross section in oriented single crystals
on the direction of the photon polarisation with respect to the crystal plane. Both a 1 mm thick single crystal of Germanium
and a 4 mm thick multi-tile set of synthetic Diamond crystals were used as analyzers of the linear polarisation.
A birefringence phenomenon, the conversion of the linear polarisation of the photon beam into circular polarisation,
was observed. This was achieved by letting the linearly polarised photon beam pass through a 10 cm thick Silicon single
crystal that acted as a ‘‘quarter wave plate’’ (QWP) as suggested by Cabibbo et al.
2005 Elsevier B.V. All rights reserved.
PACS: 29.27.Hj; 41.60.m; 42.81.Gs
| Original language | English |
|---|---|
| Pages (from-to) | 128-137 |
| Number of pages | 12 |
| Journal | Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms |
| Volume | 234 |
| Issue number | 1/2 |
| Early online date | 23 Mar 2005 |
| DOIs | |
| Publication status | Published - May 2005 |