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 AND UIC Northern Illinois University (DeKalb, IL 60115, USA) NSS 2003 Portland, Oregon

2. OUTLINE INTRODUCTION RESULTS PLANS SUMMARY NSS 2003 Portland, Oregon

3. 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 CLEALY 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. NSS 2003 Portland, Oregon

4. INTRODUCTION THE HADRON CALORIMETER WITH TRADITIONAL RESOLUTION WILL MEASURE THE ENERGY OF NEUTRAL HADRONS ONLY, WHICH, ON AVERAGE, DEPOSIT APPROXIMATLY 11% OF A JET’S TOTAL ENERGY. THUS, BECAUSE LINEAR COLLIDER DETECTOR ITSELF IS OPTIMISED 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 ENERGY RESOLUTION AND NUMBER OF HITS VERSUS THE SINGLE PARTICLE ENERGY FOR CELLS OF DIFFERENT AREAS (CELLS ARE PROJECTIVE IN  AND ). NSS 2003 Portland, Oregon

5. Energy Resolution single threshold NSS 2003 Portland, Oregon

6. N vs. E NSS 2003 Portland, Oregon

7. BY VARYING THE TRANSVERSE CELL SIZE, SIMULATIONS INDICATE THAT THE ENERGY RESOLUTION FROM DIGITAL MEASUREMENT IS 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 30 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 OCUPATION 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 2 TO 3 M, AND 4 M LONG (IN CASE OF THE SLCD). EACH 1 M2 OF ACTIVE LAYER CONSISTS OF APPROXIMATELY A THOUSAND 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

8. 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

9. EXTRUDED SCINTILLATOR IS TEN TIMES CHEAPER THAN CAST SCINTILLATOR. IT PROVIDES 60% OR MORE OF LIGHT OUTPUT WHEN COMPARED TO BC408. EXTRUDED STRIPS HAVE REGULAR DIMENSIONS AND UP TO 10 HOLES FOR WLS FIBERS INSIDE Note: Die provides exact shape and dimensions of product NSS 2003 Portland, Oregon

10. FIBERS AND SCINTILLATORS • 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. • 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. • INFLUENCE OF THE FOLLOWING SIDE AND SURFACE TREATMENTS OF SCINTILLATING CELL RESPONSES, SUCH AS POLISHING, MACHINING, MIRRORING, PAINTING AND DIFFERENT KINDS OF WRAPPING, WERE STUDIED (TABLE 1). • RESPONSES OF HEXAGONAL AND SQUARE SHAPES CELLS WITH AREA ~ 9 AND ~6 CM² WERE TESTED. CELL RESPONSES, WITH STRAIGHT AND SIGMA FIBER GROOVE SHAPES, TAPERED AND ROUND HOLE GROOVES WERE TESTED, USING WLS FIBERS EMBEDED AND GLUED WITH OPTICAL GLUE. • THE UNIFORMITY OF THE RESPONSES OF CELLS WITH STRAIGHT AND SIGMA GROOVE WERE MEASURED. RESPONSE VERSUS THICKNESS OF CELL WAS STUDIED AS WELL (THE FOLLOWING CHART). NSS 2003 Portland, Oregon

11. CELL RESPONSES WITH DIFFERENT COATING/WRAPPING THE REASON FOR CARRYING OUT THESE MEASUREMENTS WAS THE LACK OF DATA ON RESPONSE OF A SMALL SCINTILLATING CELL WITH POLISHED EDGES COMPARED TO THE RESPONSE OF A CELL WITH UNPOLISHED OR JUST MACHINED EDGES, AND HOW THESE RESPONSES ARE SENSITIVE TO DIFFERENT WRAPPING OR COATING MATERIALS. TABLE 1. RATIO OF CELL RESPONSE TO TYVEK (IN PERCENTAGES) NOTE: FOR DETAILS OF THIS MEASUREMENTS LOOK AT THE LAST SLIDE. NSS 2003 Portland, Oregon

12. 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

13. PHOTODETECTORS • THE FOLLOWING PHOTODETECTORS WERE USED FOR DIFFERENT TESTS: • VLPC, • HAMAMATSU PMT R-580, • HAMAMATSU MPMTs H8711. • ALSO, HAMAMATSU Si APD S8550 AND SiPM FROM “PULSAR” ENTERPRISE, RUSSIA ARE CURRENTLY UNDER THE TEST. NSS 2003 Portland, Oregon

14. 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 EACH CELL, MADE FROM 5 MM THICK BC408 SCINTILLATOR , HAD A HEXAGONAL SHAPE WITH 3 MM DEEP SIGMA GROOVE, 9.4 CM²; KURARAY Y-11 WLS FIBER WITH MIRROR, END WAS GLUED INSIDE AND SPLICED TO ~2 M LONG CLEAR FIBERØ 0.94 MM, TOP CHART SHOWS A MIP RESPONSE, MIDDLE AND BOTTOM CHARTS SHOW THE RESPONSE OF LED SIGNALS SIGNIFICANTLY ATTENUATED WITH FILTER TO GET SES; USING THE POISSON DISTRIBUTION THE ESTIMATED AMOUNT OF PE ARE 0.95 AND 0.6 ACCORDINGLY, MPMT SHOWS APPROXIMATELY ~10 PE. NSS 2003 Portland, Oregon

15. CONCLUSIONS THE NICADD- FERMILAB EXTRUDER HAS PRODUCED FIRST SCINTILLATING STRIPS. OPTICAL CHARACTERISTICS OF SMALL CELLS DIFFER FROM NORMAL SIZE TILE BECAUSE ATTENUATION LENGTH DOES NOT WORK; SURFACE TREATMENTS DON’T AFFECT THE RESPONSE, BUT MACHINING SIDES DO. TODAY’S DESIGN OF OPTICAL ELEMENTS CAN PROVIDE ~10 PE. WLS FIBER IS THE MOST SENSITIVE PART IN OPTICAL READOUT.CELLS, PAINTED IN ACRILIC TITANIUM WHITE, PROVIDE RESPONSE THAT IS COMPARABLE TO A CELLS WRAPPED IN TYVEK. PAINTING IS MORE PRODUCTIVE THAN WRAPPING; 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 IN FUTURE FULL-IMAGING CALORIMETRY. NSS 2003 Portland, Oregon

16.             Acknowledgments The authors are thankful to Peter Torres and Daniel Ruggiero for their help during the cell tests. We would like to thank Phill 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. NSS 2003 Portland, Oregon

17. 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 CROS-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