by Francois Piuz. Published: 20 March 2013

For some time, our section was working on pad-MWPC associated with fast RICH, promoting Cesium Iodide photocathode operated under gas. Thereby we were among the earliest contributors In ALICE for a PID system

Around 1992-3 in the ion-physics environment, we proposed with E.Nappi (Bari), G.Paic and others an impressive barrel-RICH in the ALICE frame, 230 m2of chambers.

Then at that time, R&D projects were submitted to approval, developping the new detector generation for LHC. Our team launched the RD-26 project described below:

1. Development of a Large Area Advanced Fast RICH Detector for Particle Identification at the LHC Operated with Heavy Ions (ALICE) /ALICE Collaboration The possibility to use a CsI solid photocathode (PC) in a gaseous detector [1] has stimulated a large research activity and the proposals of RICH detector systems in many future experiments [2]. The RD-26 [3] project was launched to study such a detector in the particular conditions of a heavy ion experiment at LHC (ALICE [2]).. ALICE-INT-1994-20; CERN-ALICE-INT-1994-20.- Geneva : CERN, 1994

2. Status report from the CsI-Rich Collaboration : R&D for the development of a large area advanced fast rich detector for particle identification at the LHC operated with heavy ions: RD-26 CERN-DRDC-93-36 ; DRDC-Status-report-RD-26. - 1993.

At our satisfaction, the project was accepted in 1992 meaning funding for many colleagues…

Then came the ALICE LoI (CERN-LHCC 93-16) , with still a huge barrel RICH, then the Technical Proposal (LHCC95-71). The RICH was strongly reduced in size to become the HMPID, with only 7 CsI-RICH modules (about 12m2) , being anyhow the world record of CsI-PC area...

The 2 projects were runned together, ALICE-RICH and RD-26. The goal was to develop a very flat pannel of 80x50 cm2.

It was made of a sandwich of 2 PCB (printed Circuit Board), the inner one divided into 80X40 pads of 8x8mm2 area to be covered with an evaporated (Cesium Iodide) CsI layer acting as a VUV photocathode to be operated in the gaseous medium of a MWPC. One problem was that the evaporated layer should never be in contact with air and 41 pannels had to be produced at CERN.

A history in photos...

During 1996 a detector, Proto-2, was built, achieving the 2/3 of a final module. It was thoroughly tested with entire satisfaction. The level of CsI-Quantum efficiency was found operationnal, stable and reproducible.


Then in 1998, we wrote the first Technical Design Report of ALICE, CERN/LHCC 98-19, ALICE TDR no 1, describing the whole detector and its completion.

In 2000, another prototype Proto-3 was used for single CsI-PC panel testing.

Finally in 1999-2000, one should mention that we had the opportunity to send Proto-2 at Brookhaven Lab to be used in the STAR experiment and give real physics results. It was a big challenge that turned out to be very successful.

Figure 1. Maybe a historical one...first beam T10 test with proto-2 and the first CsI-PC equipped with a few electron channels.One can see the 4 photocathode panels.

Figure 2. Major tests of proto-2 at H2-SPS in 1998. Target on the left followed by 3 pad-MWPCs to reconstruct multitrack events. Proto-2 is at the end of the line.

Quite interesting, we had the opportunity to send Proto-2 at Brookhaven Lab to be operated in the STAR experiment and make some real physics. That was a huge work but successful.

Figure 3. Proto-2 sent at Brookhaven Lab, STAR experiment in 1999. The 4 CsI-PCs had to be sent under argon circulation...Nightmare. We had 15 hours to get them back under gas flow.This is the container put in the plane, first to get out...

Figure 4. Jaap is soldering the 20 micron sense wires of the MWPC.

Figure 5. Close view of the 100 micron cathode wires of the MWPC

Figure 6. Gluing the pad-PCB on one frame of Proto-3. Has to be flat within 50 micron

Figure 7. CsI-evaporation set-up in the André Braem laboratory. The 42 PCs were evaporated here

Figure 8.Lab test using VUV Deuterium lamp and fiber optics to measure CsI-Quantum Efficienty.

Figure 9. Mounting of the 7 modules on the craddle after beam test validation

After a long time period needed to produce the 7 modules the HMPID installation into ALICE started in June 2006….

Figure 10. Transporting the 7 modules now fixed on the craddle from the assembly hall not far from the ALICE location and finally the impressive descent in the pit

Figure 11.Finally, the craddle and the 7 modules land on the platform close to the ALICE detector.

Figure 12. Some members pf the team in front of the HMPID. Eugenio Nappi with the jacket and red helmet with Giacinto de Cataldo on his left.

Figure 13. After a meeting : A.Franco, then V.Peskov is 3d from the left : E. Nappi, W. Klempt, P. Martinengo, A. di Mauro, M. Davenport, A. Gallas, J. van Bielen

Figure 14. Francois Piuz quite happy in front of Proto-2 nicely working.

Figure 15. Wonderful exemples of cherenkov rings showing more than 29 Cherenkov photons on a circle, the impact of the MIP on its center and a very clean background.