Difference between revisions of "Tagger Hall"

Revision as of 18:01, 16 September 2014

Shielding Basis for Hall D Complex (old note before shielding optimization)

Neutron background estimates in the hall

Radius of the exit electron beam pipe

Do we need a wider beam pipe transporting electrons into the dump? By Sept 2014 a 6 imch diameter pipe brought the beam to about 2m in front of the dump wall. It ends with a thick flange connected to a 1.5 inch pipe transporting the beam through the wall. There is a girder with a valve between the flange and the wall. The flange became a hot spot after the first beam tune in May 2014. Would it help to install a wider pipe from the flange through the wall?

• The deflection of the electron beam from the photon beam in this area is about L=400cm
• The electrons deflected not more than r cm from the trajectory of the non-radiated beam go into the beam dump. The others dump their energy into the hall.
• The full power of the photons is W_B·R, where W_B is the power of the electron beam and R is the radiator thickness in R.L.

The energy dumped by the radiator electrons into the hall is

W=W_B/E_o·R·∫dk·(E_o−k)/k, where E_o and k are the energies of the incoming electron and of the outcoming photon. The integral limits are E_o·(r/(L+r)), E_o

W=W_B·R·(ln((L+r)/r)−1+r/(L+r))≈W_B·R·(ln(L/r)−1+r/L)

The increase of the exit pipe radius from 2cm to 4cm would reduce the power dumped in the hall by the radiated electrons by about 15%.