1. STATUS OF MUV3 CONSTRUCTION A joint IHEP Protvino – Mainz – Pisa project MUV3  Proposed by Italo Mannelli: Thick scintillator tiles with direct light collection by PMTs through air  Design evolution to two PMT’s per tile to identify and reject early signals from Čerenkov light produced by muons crossing the PMT window ⇒ improved time resolution  Test of a cell with two PMTs on a PS beam in August 2010 (see presentation by R. Wanke at the MUV Group Meeting, 8 Sept. 2010)  Final mechanical design available at the end of 2010: frames of commercially available light Al tubes (purchased by Pisa), thin black Al septa to provide optical separation between adjacent cells, Iron plates to provide mechanical rigidity and support to the scintillating tiles and PMTs. All mechanical components, including PMT fixing collars, built in Protvino.  Almost all PMTs available from the NA48 AKL system (tested in Mainz)  Assembly of the two half-modules at CERN during November 2011 by E. Chernov, K. Kachnov (Protvino), A. Bianucci, C. Cerri (Pisa) L. Di Lella (Pisa), 14 Dec 2011

2. Sketch of the MUV3 detector 12 x 12 cells with 22 x 22 cm scintillator tiles except for the region near the beam tube where 2 x 2 cells are replaced by 8 smaller cells: in total, 148 cells (296 PMTs)

3. Scintillator tile configuration near the beam axis Half tiles → half cells become full cells when the two half modules are joined together

4. Structures of light Al tubes manufactured by Bosch (two frames connected together for each MUV3 half-module)

5. Installing the scintillator tiles Scintillator tiles are fixed to the MUV3 front plate by four special screws Temporary bar will be removed when the two half-modules are joined together

6. PMT supporting plates and light septa before installation and connection to the scintillator tile support

7. The first MUV3 half – module is (almost) completed and is moved away from the assembly tables Still missing:  additional side walls for light tightness  MUV3 “feet” with special sliding blocks to slide the two half – modules in their final positions

8. The 2 nd MUV3 half – module is completed (week of 5 December)

9. A MUV3 “foot” with one sliding block mounted on it Sliding blocks and matching rails are commercially available (Bosch) Sliding block Position of the 2 nd sliding block

10. During the week of 5 December two PMTs have been installed on one cell together with two partially overlapping scintillation counters located under half-module 1 to provide a cosmic ray trigger (I. Mannelli, A. Khudyakov) See presentation by A. Khudyakov for the results from this test

11. CONCLUSIONS  The construction of the two MUV3 half – modules is practically completed  Still missing: PMT installation (foreseen for January 2012) We need 296 PMTs – we must buy ~20 additional PMTs and bases to complete the installation for the whole MUV3 and have a few spare PMTs available during the experiment  It is planned to test all cells with cosmic rays using the final electronic chain before installation in ECN3