MICE-Note 2002-xx

June 2002

The MICE TPG project

Status and links

prepared by Alain Blondel, Uni Geneva.

This note describes the proposal of a Time Projection chamber for MICE with GEM read out. It is understood as a beginner’s introduction with the sake of providing references for those interested in the project. 

The MICE LOI submitted to PSI and RAL can be found here: 

http://proj-bdl-nice.web.cern.ch/proj-bdl-nice/cool/loi-final-ral.pdf

One can see there that the tracking devices that were considered in November 2001 were either scintillating fiber trackers or silicon trackers. A sketch of MICE with these trackers is here: http://proj-bdl-nice.web.cern.ch/proj-bdl-nice/cool/micesketchold.pdf

One of the problems of these proposals was the expected noise from photons and electrons generated by the RF cavities of the cooling section. In particular, the combination of inefficiencies in the scintillating fibers and noise made it feared that reconstruction would be seriously hampered by ambiguities. G. Barr discussed this in this note: 

http://proj-bdl-nice.web.cern.ch/proj-bdl-nice/cool/barrnoisenote.pdf

In February 2002 Ugo Gastaldi suggested that one could use a TPC with GEM readout for the trackers of MICE. The first ideas and sketches together with a possible scheme for the readout can be found in this talk:

http://proj-bdl-nice.web.cern.ch/proj-bdl-nice/talks/ugo.pdf,

or in the draft note: http://proj-bdl-nice.web.cern.ch/proj-bdl-nice/cool/gastalditpgdraft.pdf

These were presented in one of the MICE detector working groups meetings 

http://hep04.phys.iit.edu/cooldemo/detectors/detectors.html

see the March meeting:

http://hep04.phys.iit.edu/cooldemo/detectors/detectormeetingMar2002.html

This having a rather imprecise timing information (100 ns time slots at least) it would have to be complemented with at least one plane of scintillating fibers and a segmented time-of-flight system. Nevertheless, the fact that it could provide hundreds of space points along a track with potentially very small multiple scattering (for a He-isobutene filled TPG) allied with very small mass for photon conversions, make it a very interesting option. The space resolution with Helium filling needs to be evaluated. 

The readout has been discussed by Emilio Radicioni and seems to be quite OK:

http://proj-bdl-nice.web.cern.ch/proj-bdl-nice/cool/tpgemiliomarch2002.pdf

Finally the issue of pulling out the signals will have to be investigated in detail, for reasons of noise and of the relationships with the other detectors. A possible sketch of how to do this for the downstream spectrometer can be found here. 

http://proj-bdl-nice.web.cern.ch/proj-bdl-nice/cool/micesketch.pdf

What needs to be done?

The first and most urgent thing to do in my opinion is to begin the hardware test of the readout cleanliness in the vicinity of a mega-monster: the RF cavities are a mere three meters away in the MICE set up and at the time when the muons pass by there are being powered by an instantaneous power of 4 MW! this is bound to require very careful shielding of the readout system, if it can work at all. 

Also needed is a simulation of the performance of this device plugging in first the space resolution as function of drift time, then the possible effect of noise.