Sector Multipad Prototype of the FMD-MCP Detector for ALICE (1997)

We present results of the technology, manufacturing andfirst tests of a novel MCP-based sector prototypefor the Forward Multiplicity Detector for the ALICE experiment at the LHC. The detector is to provide better than sqrt<I>(M)/M</I>resolution for high multiplicity events, and about 50 pstiming resolution. Two Sector MCPs are mounted on a 200<IMG WIDTH=11 HEIGHT=18 ALIGN=MIDDLE SRC="img6.gif"> ceramics board with the multipad readout integrated with a passive summator. This microelectronics UHF device provides isochronous analogue summation of the fast 1ns signal components from 8 pads, along with the individual readout of charges. The setup is baked under 300<IMG WIDTH=6 HEIGHT=6 ALIGN=TOP SRC="img7.gif">C and then sealedinto a singular thin wall (200<IMG WIDTH=11 HEIGHT=18 ALIGN=MIDDLE SRC="img6.gif"> ) stainlesssteel vacuum sector chamber with Ti getter keeping a vacuum of 10<SUP>-5</SUP>Torr.The separation of the fast and slow componentsallows us to use this detector as the zero level trigger,in pile up and beam-gas interaction diagnostics and for thedetermination of the collision vertex along the beam axis. The results of the first and future lab and in-beam tests are discussed and presented.<P>SUMMARYThis job is a continuation of our studiesof the fast applications <A HREF="#NIM">[1]</A>for the Forward Multiplicity Detector in the ALICE experimentat the LHC <A HREF="#TP">[2]</A>Two Sector MCPs (about 18 cm<SUP>2</SUP> area) are mountedon a thin (200<IMG WIDTH=11 HEIGHT=18 ALIGN=MIDDLE SRC="img6.gif"> ) single ceramics boardwith the microelectronics design for multipad readout integrated with a passivesummator <A HREF="#MCP">[3]</A>.This UHF device provides isochronous analogue summation of thefast components of 1ns signals from 8 pads along with the individual readout of charges <A HREF="#efi">[4]</A>.The setup is assembled together with theceramic plate which integrates multichannel feedthroughsand one cylinder Ti-getter pump specially developed forthis detector. This ceramic plate is welded to the stainless steel vacuum sector chamber.Special Al coating is applied on the inner side of the 200 micronthick chamber walls in order to prevent hydrogen diffusion. The whole setup is baked under 300<IMG WIDTH=6 HEIGHT=6 ALIGN=TOP SRC="img7.gif">C ,a getter Ti pump is activated, and then the chamber is hermetically sealed, providing the working vacuum of 10<SUP>(-5)</SUP>Torr. The separation of the fast and slow signal components which is done by passive summatorallows us to use this detector as the zero level trigger, in pile-up and beam-gas interaction diagnostics and for thedetermination of the collision vertex position along the beam axis <A HREF=#TP">[2]</A>, <A HREF="#efi">[4]</A>.Small area (1 cm<SUP>2</SUP>) prototype detectors were widely used during the initial stages of the technological developments.Vacuum tests were performed: degassing rates were studied for the stainless steel thin wall chamber , Ti getter, MCPs and ceramics board and feedthroughs. UHFstudies confirmed the technological feasibilities of the passive summator and feedtroughs design with the useful frequency range up to 1.1GHz.First in-beam studies were done at the low energy university cyclotron. Future in-beam tests are also planned.<P>Abstract:This job is supported by the International Science andAbstract:Technology Center, Grant No.345.<P>Acknowledgements<A NAME="NIM">[1] G.Feofilov et al., NIM A367 (1995) 402-407</A><A NAME="TP">[2] N.Ahmad et al., "ALICE Technical Proposal ", CERN/LHCC/95-71, LHCC/P3, 15 December 1995, chapters 7 and 9.</A><A NAME="MCP">[3] G.Feofilov et al.,ALICE Int. Note/MCP,95-39,16/11/95</A><A NAME="efi">[4] L.Efimov, G.Feofilov et al., 2nd-Workshop on Electronics for LHC Experiments, Balatonfured,Hungary, September 23-27, 1996;p.166-169CERN/LHCC/96-39, 21 October 1996</A><P>