R&D on a new construction technique for W/ScFi calorimeters. O. Tsai (UCLA), Calor Santa Fe. June 5, 2012

The basic idea behind this technique is simple – mix together W powder and Sc. Fibers. Take 1, Short and pure technology R&D (not targeted any specific experiments). Key words: Compact electromagnetic calorimeters, Good energy resolution, Readout in the magnetic field, Simple and Cost effective construction technique. First prototype was constructed in couple of months (4 x 4 matrix, sampling fraction 1.2%, 496 BCF12 square 0.25mm x 0.25mm fibers per tower, final density ~11g/cm 3,readout APDs and mesh PMTs) Test Run, SLAC T466, > the main result Go back and do your home work, then return!

Importance of homogeneity was understood and technique was changed accordingly. First, form a matrix from fibers (use intermediate meshes), second pour W powder into this matrix, third replace air with epoxy. Take 2. New small 3x4 new matrix was built, test run was scheduled at SLAC in 2004, but was first delayed and later canceled due to an accident at SLAC. The future development was postponed till 2011 for a multiple of different reasons.

RHIC NSRL LINAC Booster AGS Tandems STAR 6:00 o’clock PHENIX 8:00 o’clock (PHOBOS) 10:00 o’clock Polarized Jet Target 12:00 o’clock RF 4:00 o’clock (BRAHMS) 2:00 o’clock EBIS BLIP RD1, Development of a new detector technology for fiber sampling calorimeters for EIC and STAR. May 9, 2011 (UCLA,Texas A&M, Pennsylvania State University) Electron Ion Collider Generic Detector R&D. BNL & JLAB 1.Calorimetry for EIC 2.STAR Forward Upgrade 3.Some similar conceptual requirements. 4. New Generic Detector R&D Program Made Take 3 possible in 2011.

The motivations for this R&D: Develop simple, cost effective, flexible techniques to build compact sampling calorimeters with good characteristics. In year 1 we wanted to get “proof of principle” with the construction and beam test of prototypes. One prototype is straightforward continuation of development started in 2003 (wiggled fibers, thus the name SPACORDION ) Second prototype with straight fibers (for simplicity called SPACAL ).

Construction steps: 1. Put fibers in set of screens. 2. Spread meshes and put assemblies in container. 3. Epoxy both ends (photodetector and mirror end) 4. Fill container with W powder. 5. Replace air in detector with epoxy.

“How to make your own pie”

Prototypes. Spacordion. Not There Yet! SPACORDION was the first prototype. We build it using technique we developed in the past. Each tower were glued from four subassemblies. Then all 16 towers were glued to a single matrix. The fibers were bundled at the end. Main problem with this approach is: matching four pieces to make a single tower. It was quite labor extensive process. Not that Simple. So, we refine technique for second prototype.

Prototypes. SPACAL. This what we wanted! Parameters: Final Density g/cm 3, X 0 ~ 7 mm, R m ~ 2.3 cm, S f -2% (electrons), Sc. Fibers -SCSF78 Ø 0.47 mm Spacing 1 mm center-to-center. Supermodule 2x2 towers. Details: Dimensions 16.6 × 5.33 ×5.33 cm 3 Weight of supermodules (4567, 4651, 4627,4630 g.) Number of fibers Resolution ~12%/√E (GEANT4) Light collection. Acrylic light guide + ESR mirror pipe. PMT – Electron Tube 9125B Optical contacts, BC-600, BC X 0 The front face mirror was made from ESR coupled with BC-630 This was the weakest link (uniformity) going to the test run.

Test Run, FNAL MTBF (Jan , 2012) Main Goals: 1. Get “proof of principle”, i.e. measure energy resolution, uniformity of response, and compare to MC. 2. Measure the light yield. ( defines direction for year 2 R&D)

T1018, Test Run. What was measured ? Resolution Raw number Beam Absolute Scale, dp/p Detector Sampling Fluctuations Photostatistics Non- uniformities Light Collection Non-uniformity of tower composition Attenuation Length Mirror quality (fiber-to-fiber variations) Light guide/coupling to PMT

T1018 It works! 1.Resolution is close to expected. 2.Light yield is good ~ 2000 Phe/GeV (are all these 2000 Phe good one?) Also measured: 1.Uniformity of response across the towers. 2. Energy resolution with and without mirror. 3. Perform scans along the towers with electrons and muons. 4. Estimated effects of attenuation and towers non-uniformities on resolution.

Uniformity of response across the tower. Test Run. 4 GeV electrons. Each square is 4.8 mm x 4.8 mm, selected by Sc. hodoscope. Uniformity of SPACAL response is 1.4%

Longitudinal Scans, Electrons 8 GeV and MIPs. SPACAL 1 SPACAL 2 SPACAL 3 SPACAL 4 Beam 4 cm 21 cm

Attenuation lengths and uniformity along the towers. MIPs Electrons 1. Typical attenuation length for 0.5 mm fibers (no damage due to packing). 2. Non-uniformities inside the towers is ~ 5% in the most important region from 5-14 Xo. 3. Attenuation length measured with electrons is ~ 3 times shorter compare to one measured with MIPs. <- That was not planned! 4. SPACORDION attenuation length is ~50% of SPACAL, as well as light yield. Do Not use very thin fibers (0.33 mm in SPACORDION vs 0.47 in SPACAL). 300 mkm brass meshes.

R&D Year1. Summary 1. “Proof of Principle” demonstrated. Energy resolution, uniformities across and along the towers, and light yield measured during test run all close to what was expected. Parameters of SPACAL already good enough for STAR Forward Upgrade (EM section). R&D program for Year 2 streamlined.

R&D plan for Year 2. STAR, EIC. Mechanical questions (properties of the compound, effects of stress on fibers, etc.) STAR,EIC. Compact readout with APDs and SiPMTs. EIC. Extension of this technique for wedge type towers. (variable Sf may be not prohibited, but requred?) STAR. TDR forward calorimeters upgrade. EIC. progress from conceptual to realistic requirements for dedicated detector calorimeters.

“Acceleration !” Let’s keep filling this plot! The End ! Thank you!

Backup slides.

SPACORDION Attenuation length, electrons 8 GeV.

Backup slide.

Wiggle or not is a question. However for some applications where channeling is an issue this will help. Plus: Increased sampling frequency for given number of fibers. More fibers will contribute to a signal, thus fiber-to-fiber variations will be diminished. Minus: It is reasonably easy to wiggle 370 fibers of 0.33 mm diameter, more than that will be a problem. From M.Livan “The art of Calorimetry, Lecture iV”