photon beam

The photon target - setup

To produce a "pure" photon beam, the straight beam line of H8 is used towards the ATLAS test area. A short target located downstream of the cherenkov counter (XCET042534) is submitted to the secondary beam from T4 in order to maximise em/h shower. Bend 4 of the VLE beam line is used to speperate the photons and the electrons in space. The desired lateral displacment at the downstream end of Morpurgo magnet should be 10 cm. The maximum beanding power of the MBPL of 3.8 Tm results in a maximum momentum p=299.9/Theta*B*l =165 GeV/c of the secondary beam. The geometrical layout indicates the length of the elements along the beam line. The particle production at the photon converter could like like this.

Production beam

In order to minimise the hadronic content of the secondary beam, the filter mode will be use, which enables the seperation of leptons and hadrons. The secondary (p~150 GeV/c) beam of T4 is directed towards the filter target, which is placed between the two bends of the large spectrometer. WIth the bend 3/4 of the spectrometer the leptons of an momentum below the secondary one is chosen and directed towards the photon target mentioned above. This provides a pure electron beam. It is as well possible to produce an electron beam by synchrotron losses, where the electron beam is contaminated by about 30% pions, but at the same time has a higher intensity. This second mode is only possible well above 100 GeV/c. The picture below indicates the shema of the H8 beam line. Target T48 (VLE) is out of beam (=not used).

With these optics (magnet settings) a TURTLE simulation shows the spot size at the converter. This is indicating the spot size and divergence at full acceptance.