TOWARDS A SCINTILLATOR BASED DIGITAL HADRON CALORIMETER FOR THE LINEAR COLLIDER DETECTOR

1. TOWARDS A SCINTILLATOR BASED DIGITAL HADRON CALORIMETER FOR THE LINEAR COLLIDER DETECTOR ALEXANDRE DYCHKANT FOR NICADD/NIU Northern Illinois University (DeKalb, IL 60115, USA) NSS 2003 Portland, Oregon

2. INTRODUCTION THE CURRENT TEVATRON RUN AT FERMI NATIONAL ACCELERATOR LABORATORY AND OPERATION OF THE LARGE HADRON COLLIDER AT CERN ARE CLEAR PRIORITIES FOR THE PRESENT AND IMMEDIATE FUTURE OF THE HIGH-ENERGY PHYSICS FRONTIER. HOWEVER, NOW IS A GOOD TIME TO PLAN AND PREPARE FOR THE NEXT STEP, A LINEAR E+E- COLLIDER, TO REVIEW TECHNOLOGIES FOR DETECTORS, AND TO CLEARLY POINT OUT AREAS WHERE R & D WILL BE NEEDED IN THE FUTURE. IN ORDER TO REALIZE THE FULL POTENTIAL OF A FUTURE LINEAR ELECTRON POSITRON COLLIDER, A DETECTOR SHOULD HAVE A HADRON CALORIMETER WITH A DIJET ENERGY RESOLUTION 30%/E OR BETTER. MOST MODERN SAMPLING HADRON CALORIMETERS HAVE ~90%/E ENERGY RESOLUTION FOR JETS WHICH CAN BE IMPROVED UP TO ~50%/E USING FLOW ENERGY ALGORITHMS. HOWEVER, IF ENERGY FLOW ALGORITHMS ARE APPLIED TO A DETECTOR THAT HAS A HIGHLY SEGMENTED HADRON CALORIMETER, THE HITS FROM CHARGED PARTICLES CAN BE SEPARATED FROM NEUTRAL PARTICLES IN A STRONG MAGNETIC FIELD BY ASSOCIATION WITH CORRESPONDING TRACKS IN THE INNER VOLUME. AFTER THAT, THE TRACKER WILL BE USED TO MEASURE THE CHARGED COMPONENTS, AND THE ELECTROMAGNETIC CALORIMETER WILL BE USED TO MEASURE THE PHOTONS. EACH OF THEM PROVIDE HIGH PRECISION ENERGY MEASUREMENTS. THEHADRON CALORIMETER WITH TRADITIONAL RESOLUTION WILL MEASURE THE ENERGY OF NEUTRAL HADRONS ONLY, WHICH, ON AVERAGE, DEPOSIT APPROXIMATELY 11% OF A JET’S TOTAL ENERGY. THUS, BECAUSE LINEAR COLLIDER DETECTOR ITSELF IS OPTIMIZED FOR ENERGY FLOW ALGORITHMS, A NET JET ENERGY RESOLUTION OF 30%/E COULD BE ACHIEVED. THE NEXT TWO SLIDES WILL PROVIDE THE RESULTS OF THE SIMULATIONS OF NUMBER OF HITS AND ENERGY RESOLUTION VERSUS THE SINGLE PARTICLE ENERGY FOR CELLS OF DIFFERENT AREAS. NSS 2003 Portland, Oregon

3. NUMBER OF CELLS VS INCIDENT E NSS 2003 Portland, Oregon

4. ENERGY RESOLUTION NSS 2003 Portland, Oregon

5. BY VARYING THE TRANSVERSE CELL SIZE, SIMULATIONS INDICATE THAT THE ENERGY RESOLUTION FROM DIGITAL MEASUREMENT CAN BE BETTER THAN CORRESPONDING ANALOG MEASUREMENTS. THIS SUPPORTS DIGITAL APPROACH TO THE HADRON CALORIMETRY, AND FUTURE RESEARCH ON ENERGY FLOW ALGORITHMS SHOULD INCLUDE OPTIMIZATIONS FOR DIGITAL HADRON CALIRIMETER AS WELL. OUR GROUP AT THE NORTHERN ILLINOIS CENTER FOR ACCELERATOR AND DETECTOR DEVELOPMENT (NICADD), AS A POSSIBLE SOLUTION, HAS UNDERTAKEN A COMPREHENSIVE FEASIBILITY STUDY OF A SAMPLING HADRON CALORIMETER WITH SMALL SCINTILLATING CELLS AND 34 LAYERS OF ACTIVE MEDIUM. THE PROJECT CONSISTS OF COMPUTER-BASED SIMULATIONS AND THE PROTOTYPE, DEVELOPED CONCURRENTLY. THIS TYPE OF CALORIMETER WILL HAVE UP TO 5 MILLION INDEPENDENT PHOTO READOUT CHANNELS. BECAUSE THE AVERAGE OCCUPATION OF CELL WILL BE LESS THAN ONE, IT CAN BE A DIGITAL SINGLE BIT READOUT WITH THE THRESHOLD SET TO DETECT THE PASSAGE OF A MINIMUM IONIZING PARTICLE (MIP). IT IS A PROVEN TECHNOLOGY, BUT THE SCALE OF ITS APPLICATION IS QUITE INNOVATIVE. EACH ACTIVE LAYER OF THE CALORIMETER HAS A CYLINDRICAL SHAPE, WITH RADII FROM 1.44 TO 2.46 M, AND 5.72 M LONG (IN CASE OF THE SLCD). EACH 1 M2 OF ACTIVE LAYER CONSISTS OF APPROXIMATELY A THOUSAND IDENTICAL CELLS. EACH CELL HAS A WLS FIBER THAT CAN BE CONNECTED TO A PHOTODETECTOR DIRECTLY (INSIDE THE MAGNETIC COIL), OR VIA CLEAR FIBER (OUTSIDE THE MAGNETIC COIL). IN THE LAST CASE, AN ADDITIONAL GAP OF 3 MM FOR CLEAR FIBER ROUTING WILL BE NEEDED. NSS 2003 Portland, Oregon

6. NICADD PROTOTYPE OF SDHCAL Scintillating Digital Hadron Calorimeter (SDHCAL) consists of the following major optical parts: scintillating cells, optical fibers, and photo detectors. For the prototype, we thoroughly investigated the response of the cells with dimensions close to the Moliere radius (~17 mm) for a passive material used (that can be brass or stainless steel). We are going to use extruded scintillator to reduce the cost. Fibers and photo detectors can be the most expensive part of this project. In this presentation I’m going to show that the small scintillating cells are a reasonable approach to DHCAL. NSS 2003 Portland, Oregon

7. FIBERS, SCINTILLATORS, AND PH OTODETECTORS • THE FOLLOWING SCINTILLATORS WERE TESTED: • BICRON BC-408 5, 10, AND 20 MM THICKNESSES; • ELJEN TECHNOLOGE EJ-200 3, 4, AND 5 MM THICKNESSES; • NICADD-FERMILAB EXTRUDED 5 MM THICKNESS. IT PROVIDES ~60% OUTPUT OF BC-408. • INFLUENCE OF THE SIDE AND SURFACE TREATMENTS, SUCH AS POLISHING, MACHINING, MIRRORING, PAINTING AND DIFFERENT KINDS OF WRAPPING, ON THE CELL RESPONSE WERE STUDIED (TABLE 1-3). • RESPONSE VERSUS THICKNESS OF CELL WAS STUDIED AS WELL (THE FOLLOWING CHART). • RESPONSES OF HEXAGONAL AND SQUARE SHAPES CELLS WITH AREA ~ 9 AND ~6 CM² WERE TESTED. • CELL RESPONSES, WITH STRAIGHT AND SIGMA SHAPES FIBER GROOVE, TAPERED AND ROUND HOLE GROOVES WERE TESTED, USING WLS FIBERS EMBEDED AND GLUED WITH OPTICAL GLUE AS WELL. • THE UNIFORMITY OF THE RESPONSES OF CELLS WITH THE STRAIGHT AND SIGMA GROOVE WERE MEASURED. NSS 2003 Portland, Oregon

8. TABLE 1. NORMALIZED CELLS RESPONSES FOR DIFFERENT COATING OR WRAPPING TABLE 2. RATIO OF RESPONSES FOR CELLS WITH UNPOLISHED SIDES TO THE RESPONSE OF CELLS WITH POLISHED SIDES TABLE 3. NORMALIZED RESPONSES OF CELLS FOR DIFFERENT KIND OF SURFACE TREATMENTS NOTE: FOR DETAILS OF THIS MEASUREMENTS LOOK AT THE LAST SLIDE. NSS 2003 Portland, Oregon

9. THIS CHART REPRESENTS RESPONSE OF CELLS WITH THICKNESSES of 3, 4, AND 5 MM. UNITS FOR THICKNESS AND RESPONSE WERE NORMALIZED TO CELL WITH 3 MM THICKNESS IN ORDER TO SIMPLIFY THE FOLLOWING ANALYSIS. Cs-137 RADIOACTIVE SOURCE WAS USED. THE RESPONSE IS A LINEAR FUNCTION OF CELL THICKNESS UP TO 5 MM WITH THE SLOPE OF 0.84. NSS 2003 Portland, Oregon

10. FIBERS, SCINTILLATORS, AND PHOTODETECTORS • THE FOLLOWING FIBERS WERE TESTED: • BICRON BCF-92 SQUARE, 0.8 MM SIDE; • BICRON BCF-92 ROUND, 0.8 MM OUTER DIAMETER; • BICRON BCF-92 ROUND, 1.0 MM OUTER DIAMETER; • KURARAY Y-11 ROUND, 0.94 MM OUTER DIAMETER • KURARAY Y-11 ROUND, 1.0 MM OUTER DIAMETER; • (KURARAY CLEAR ROUND, 0.94 MM OUTER DIAMETER.) • ALL FIBER ENDS WERE POLISHED USING FLY DIAMOND CUTTING TECHNIQUE. • ONE END OF EACH WLS FIBER WAS ALUMINUM MIRRORED. • ALL WLS FIBERS WERE 1 M LONG. • THERMAL SPLICING FOR KURARAY ROUND 0.94 MM OUTER DIAMETER FIBERS WAS SUCCESSFULLY RE-TESTED BY FOLLOWING THE CMS PROCEDURE. • KURARAY Y-11 ROUND, 1.0 MM OUTER DIAMETER WLS FIBERS PROVIDE THE LARGEST RESPONSE, WHICH IS 3.14 TIMES LARGER THAN OUTPUT OF BCF-92 SQUARE 0.8 MM SIDE WLS FIBER. NSS 2003 Portland, Oregon

11. PHOTODETECTORS • THE FOLLOWING PHOTODETECTORS WERE USED FOR DIFFERENT TESTS: • VLPC, • HAMAMATSU PMT R-580, • HAMAMATSU MPMTs H8711. MEASUREMENTS WITH H8711 COSMIC TRIGGER PROVIDES PARTICLES WITH TRACKS PERPENDICULAR TO THE STACK OF CELLS; 2  OF BRASS ARE INSTALLED BETWEEN THE LAYERS; WE USE VME CRATE WITH QDC V792 AND LABVIEW DAQ TOP CHART SHOWS A MIP RESPONSE, BOTTOM CHART SHOWS THE RESPONSE OF LED SIGNALS SIGNIFICANTLY ATTENUATED WITH FILTERS TO GET SINGLE ELECTRON SPECTRUM. MPMT SHOWS APPROXIMATELY ~10 PE. NSS 2003 Portland, Oregon

12. NEW PHOTODETECTORS ALSO, HAMAMATSU Si APD S8550 AND SiPM FROM “PULSAR” ENTERPRISE, RUSSIA ARE CURRENTLY UNDER THE TEST. NSS 2003 Portland, Oregon

13. NSS 2003 Portland, Oregon

14. CONCLUSIONS • TODAY’S DESIGN OF OPTICAL ELEMENTS CAN PROVIDE ~10 PE. • OPTICAL CHARACTERISTICS OF SMALL CELLS DIFFER FROM NORMAL SIZE TILES BECAUSE ATTENUATION LENGTH DOES NOT WORK. SURFACE TREATMENTS DON’T AFFECT THE RESPONSE, BUT MACHINING SIDES DO. • CELLS, PAINTED IN ACRYLIC TITANIUM WHITE, PROVIDE RESPONSE THAT IS COMPARABLE TO A CELLS WRAPPED IN TYVEK, PAINTING IS MORE PRODUCTIVE THAN WRAPPING, AND CROSSTALK BETWEEN WHITE PAINTED CELLS IS SMALL. • THE NICADD PROTOTYPE OF SDHCAL IS BEING TESTED USING COSMICS RAYS; • NEW PHOTODETECTORS WILL BE USED IN THIS STUDY AND NEED FURTHER R&D. • DIGITAL HADRON CALORIMETER WITH SMALL SCINTILLATING CELLSIS A • PLAUSIBLE SOLUTION FOR THE FUTURE LINEAR COLLIDER DETECTOR. • FURTHER R&D IN SCINTILLATING DIGITAL HADRON CALORIMETRY OPENS NEW OPPORTUNITIES FOR FULL RECONSTRUCTION EVENTS IN FUTURE DETECTOR. NSS 2003 Portland, Oregon

15.             Acknowledgments The authors are thankful to Peter Torres and Daniel Ruggiero for their help during the cell tests. We would like to thank Phil Stone who provided excellent mechanical support.                 References [1] C.Damerell et al., pg. 431, and J.Brau et al., pg. 437, Proc. Swnowmass 1996. [2] O. Lobban et al., On the Energy Measurement of Hadron Jets, Proceedings of the Tenth International Conference on Calorimetry in Particle Physics, Pasadena, 2002. World Scientific, Singapore, 2002, p.814-833. [3] TESLA Technical Design Report, DESY, March 2001. [4] SAINT-GOBAIN (Bicron), 12345 Kinsman Road, Newbury, OH 44065, USA. [5] CMS The Hadron Calorimeter Project Technical Design Report CERN/LHCC 97 CMS TDR 2, 20 June 1997. [6] HAMAMATSU CORPORATION, 360 Foothill Road, P.O.BOX 6910, Bridgewater, NJ 08807-0919, USA; 314-5, Shimokanzo, Toyooka-village, Iwata-gun, Shizuoka-ken, 438-0193 Jap1. [7] Keithley Instruments, Inc., 28775 Aurora Road, Cleveland, OH 44139, USA. [8] The MINOS Detectors Technical Design Report. NuMI-L-603, March 1, 1999. [9] A. Bross et al., The Digital Hadron Calorimeter (DHC) Elements Test, FERMILAB-TN-733, April 2003. [10] Kuraray America Inc., 200 Park Ave, NY 10166,USA; 3-1-6, NIHONBASHI, CHUO-KU, TOKYO 103-8254, JAPAN. [11] “Pulsar” Enterprise, Okruzhnoj Proezd 27, Moscow, Russia. [12] ELJEN TECHNOLOGY, PO Box 870, 300 Crane Street, Sweetwater, Texas 79556, USA. NSS 2003 Portland, Oregon

16. CELLS RESPONSE TO DIFFERENT COATING/WRAPPING THE REASON FOR CARRYING OUT THESE MEASUREMENTS WAS THE LACK OF DATA ON THE RESPONSE OF A SMALL SCINTILLATING CELL WITH POLISHED EDGES COMPARED TO THE RESPONSE OF A CELL WITH NON-POLISHED OR JUST MACHINED EDGES AND HOW ARE THESE RESPONSES SENSITIVE TO DIFFERENT WRAPPING OR COATING MATERIALS. GEOMETRY, MATERIALS, AND TOOLS CELL MATERIAL SCINTILLATOR BC408, THICKNESS 5 MM, SHAPE HEXAGON, AREA- 9.4 CM², 5 CELLS HAVE FINISHED EDGES; ALL TOTAL-11 CELLS. GROOVE SIGMA SHAPE, RADIUS 12 MM, 25º OF CIRCLE WITHOUT GROOVE, RECTANGULAR CROSS-SECTION, WIDTH 1 MM, DEPTH 4.5 MM AND TAPERED TO EXIT. WLS FIBER BCF92, SQUARE, SIDE 0.8 MM, LENGTH- 1 M,FINISHED ENDS, ONE END MIRRORED, EMBEDDED AND GLUED INTO THE GROOVE USING BC600. WRAPPING MATERIALS TYVEK, 3M CM500, 3M CM590, 3M VM2002, ALUMINIZED MYLAR, TITANIUM WHITE ACRYLIC PAINT FROM LIQUITEX ENGLAND, (ALUMINUM FOIL). PHOTOMULTIPLIER TUBE HAMAMATSU R580, HIGH VOLTAGE 1300V, DARK CURRENT LESS THAN 0.07 NA, OR LESS THAN 0.1% WITH Sr90 (2 mC) Note: Painting is the most attractive solution because of high productivity. NSS 2003 Portland, Oregon

17. THANK YOU VERY MUCH FOR YOUR ATTENTION. NSS 2003 Portland, Oregon