1. A General High Resolution Hadron Calorimeter using Scintillator Tiles Manuel I. Martin for NIU / NICADD Northern Illinois University Northern Illinois Center for Accelerator and Detector Development

2. August 2002Manuel I. Martin 2 GOALS Design a DHC (Digital Hadron Calorimeter) using Scintillating Tiles with overall minimum cost. Build a prototype of the DHC to test it on a test beam. SUB GOALS Find the optimal geometry for the tiles Find the optimal geometry for the groove (for WLSF) Find the optimal geometry for the DHC Find the ‘best’ choice for the absorber material Find a suitable method to ‘make’ the tiles, embed the WLSF, make the transition from WLSF to CF, route the CF out of the DHC volume Design the ‘minimal’ electronics required for the DHC

3. August 2002Manuel I. Martin 3 Understanding the Geometry Tessellation of the plane with identical polygons Using ‘identical’ polygons we can ‘cover’ a plane with six basic different patterns using triangles, rectangles or hexagons as shown below Patterns T a, T b and H a generate new patterns by stretching the plane along one of the axis. TaTa TbTb RaRa RbRb RcRc HaHa u v u v u v u v u v u v

4. August 2002Manuel I. Martin 4 Optimizing the Geometry for the Tiles As the tiles are made smaller, edge effects and lack of uniform response become quite important. On first approximation, the edge effect is proportional to the perimeter of the cell and its height, and inversely proportional to its area. There are only three convex shapes which could be used to ‘cover’ a surface. For equal cell height, the ratio [Perimeter]/[Area] gives a measure of the edge effect:  Triangle 4* 3 ½ / a  Rectangle 4 / a 4*a*b / (a+b)  Hexagon 4 / (a* 3 ½ )

5. August 2002Manuel I. Martin 5 Optimizing the Geometry for the Groove We made several hexagonal cells with different groove shapes and depths. After measuring the light output for each configuration, we selected two groove configurations as most promising: Straight Groove (Simplest design) Sigma Groove (Provides optimal uniform response) length ≈ 38mm width ≈.2mm more than the WLSF diameter depth ≈ 3mm length ≈ 85mm same width and depth

6. August 2002Manuel I. Martin 6 Surface Covering for the Cells To obtain the maximum light output from a scintillating cell, the surface should be covered by some material. This cover should create a diffusing/reflecting media. A well - known way to achieve this is by wrapping the scintillating cell in white Tyvek material. Unfortunately, this is a labor- intensive process and, thus, unsuitable for the task involving one million or more cells. The NIU/NICADD team has tested several alternatives to Tyvek wrapping with interesting results

7. August 2002Manuel I. Martin 7 Comparative Light Output Measurements All measurements were made under the same conditions. Source Sr-90 Hexagonal Cell l=19mm h=5mm Scintillator BC-408 WLSF BCF-92 Ø1mm (mirrored) Groove 1.2x3x37mm Fiber Length 400mm Attenuation length ~4000mm PMT 16% Q efficiency Surface Covering for the Cells Surface TreatmentnA output % WrappingTyvek1000.9 100 Aluminized Mylar Tape 465.9 46 Spray Painting Vinyl473.747 Lacquer439.443 Acrylic816.782 SputteringAl233.523

8. August 2002Manuel I. Martin 8 “Direct” Light Output Measurements CELL WLSF CF Optical Grease Transfer VLPC AMPLIFIER ADC Cosmic rays ▲ TYVEK Wrapping WLSF ~400 mm CF ~1500 mm VLPC ~85% QEF ~70K Gain ~ 9°K Gain correction 1.8 PE Tyvek ~ 30 (Direct) Acrylic ~ 25 (Calculated) PE Tyvek ~ 30 (Direct) Acrylic ~ 25 (Calculated)

9. August 2002Manuel I. Martin 9 Support material Inner Ring: Tungsten at least 5mm Outer Ring: Aluminum structure Radial (ends): Aluminum structure Cell Geometry Hexagonal base Prism 19mm side Scintillator Material BC-408 5mm thick Absorber Material Brass 20.2mm thick Fiber Material WLSF >> Y-11 (Kuraray) [BCF-92] CF >> Kuraray [BCF-98] Fiber Geometry Ø.9 mm mirror end.64mm 2 ( R ) Groove Geometry Sigmoid (length ≈ 83mm) Reflector Material Painted (Acrylic White Titanium Dioxide) Preliminary Design Expected Yield ~ 25 PE/MIP

10. August 2002Manuel I. Martin 10 DHC DESIGN CHOICES Architecture Not Projective Projective Projective on φ Projective on φ and η Single Tower Multiple Towers Single Tower Multiple Towers Number of cells and shapes is function of the chosen architecture

11. August 2002Manuel I. Martin 11 General Structure of ‘Cells’, ‘Towers’ and ‘Layers’ for the CDHC using the SD Mar 01 as Model AbsorberScintillating Tile WLSF 2mm GAP Number of Layers 38 Number of Towers 4 (# layers per tower 10+10+10+8) Inner Radius of first Tower 1528 mm Number of Cells along φ 170 Total # of Cells in Tower Cylinder 321,300 Inner Radius of second Tower 1794 mm Number of Cells along φ 200 Total # of Cells in Tower Cylinder 378,000 Inner Radius of third Tower 2066 mm Number of Cells along φ 230 Total # of Cells in Tower Cylinder 434,700 Inner Radius of fourth Tower 2338 mm Number of Cells along φ 260 Total # of Cells in Tower Cylinder 321,300 Total # of Cells in the CDHC 1,527,120 First Absorber Layer ~ 14 mm of Tungsten All other Absorber layers ~ 20 mm of Brass Support outer ring ~ 29 mm (Al structure)

12. August 2002Manuel I. Martin 12 ENERGY RESPONSE OF THE CHDC Mono-energetic 10GeV Charged Pions Origin [0, 0, 0] Aimed at [R, 0, 0] Infinite Resolution CDHC Real CDHC with ~9.2 cm 2 Hexagonal Cells

13. August 2002Manuel I. Martin 13 Total (EM+HAD) energy for the 10 GeV pions Using GIGS with NICADD proposed detector

14. August 2002Manuel I. Martin 14 NOTES The simulation plots shown were generated with GIGS (Geometry Independent G4 based Software), the software package that NICADD is developing. For details see my software presentation at this workshop or go to: http://nicadd.niu.edu/~manuel/Software_01.ppt This presentation is posted on: http://nicadd.niu.edu/~manuel/Hardware_01.ppt For more details about this and other LC and LCD related works at NICADD go to: http://nicadd.niu.edu

15. August 2002Manuel I. Martin 15 CONCLUSIONS We have designed a DHC using Hexagonal Scintillating Tiles which has the following characteristics: »Excellent response ~ 25 PE/MIP »No Cracks »Optimized for economical production »Highly segmented PLANS Build Towers for prototype testing Test on Beam Line Optimize cell size and construction techniques Simulate response using GIGS (see my talk on Software)