NO A at Caltech Leon Mualem DOE Review July 25, 2007

The NO A Detector ~80 m 15.7 m  ~16 kT total mass  “Totally Active” granular design  Outstanding e pattern recognition & measurement  Alternating X and Y views  12 Extruded PVC Modules per plane  32 Individual cells per Module, so 384 Cells per plane Working to fit 260M AY$ TPC cap

NO A Tasks Caltech Initiated or Responsible for many aspects of NO A  Hardware  DAQ/Electronics Management  APD Testing  PVC Testing  Fiber Testing  Vertical Slice Tests  Software  Framework Development  Subshower Package  Photon Transport simulation  Supernova Sensitivity

Overview of Detector R&D NO A  Perform light output tests to understand the components of the scintillator system [Ongoing]  PVC extrusions, liquid scintillator, WLS fiber  Verification of scintillator system performance using a NO A APD [Ongoing]  Photon production and transport Monte Carlo [Ongoing]  Personnel – Jason Trevor, Leon Mualem + undergraduate

NO A Scintillator System  Each cell an extruded TiO 2 loaded PVC tube with ID 60mm x 39mm x 15.7m long  Cells are filled with mineral oil scintillator which is read out at one end with a U-loop WLS fiber running to a multi-pixel APD  Kuraray 0.7 mm WLS Fiber  Light output requirement determined by achievable noise on the APD amplifier. The current estimate of minimum required Light Output is ~20-25 photoelectrons One Cell 0.7mm WLS Fiber R&D at Caltech  Composition of the PVC cell walls  Liquid scintillator composition  Fiber diameter and dye concentration  Fiber position  Integration testing

Interface and Readout Electronics Box

32 Pixel APD Photodetector Array Manufacturer Pixel Active Area1.95 mm × 1.0 mm Pixel Pitch2.65 mm Array Size32 pixels Die Size15.34mm × 13.64mm Quantum Efficiency (>525 nm)85% Pixel Capacitance10 pF Bulk Dark Current (I B ) at 25 C12.5 pA Bulk Dark Current (I B ) at -15 C0.25 pA Peak Sensitivity600 nm Operating Voltage375 ± 50 volts Gain at Operating Voltage100 Operating Temperature (with Thermo-Electric Cooler) -15 º C Expected Signal-to-Noise Ratio (Muon at Far End of Cell) 10:1 APD channels per plane384 APD arrays per plane12

APD Photodetector  Si Avalanche Photodiode  Custom design to match two-fiber aspect ratio  Bare die mounted to PCB via gold bump thermo- compression

Scintillator System R&D  Liquid Scintillator  Two competing mineral oil vendors (Parol, Ren)  Competing vendors for additives  Concentration of additives (pseudocumene, PPO, Bis-MSB)  PVC Extrusions  Three competing PVC formulations (Prime, Aurora, NOvA collaboration)  Two types of TiO 2 (Anatase, Rutile)  Competing factors (extrudability, reflectivity, structural issues)

Test Setup PMT M16 PMT Box “  Cell” Lead Scintillating Disc 1.2mm Clear Fiber  We are currently using a “NO A Cell” with internal dimensions 38.5mm x 60mm x 85cm.  Each end of the fiber “U” is connected to an individual pixel on an M16 phototube by 3.5m of 1.2mm clear fiber.  Fibers are held in a fixed position inside the cell by a pair of acrylic “spiders.” (More on this later)  For testing purposes I am using vertical muons from cosmic rays.  The cosmic ray muon telescope consists of two circular discs (~4 cm diam) separated by 14 cm and 1 inch of lead.

The “NO A Cell” PVC 60mm “NO A Cell” 38.5mm  The “NO A Cell” is actually a rectangular aluminum tube which is lined on the inside with the PVC we are testing.

More “NOvA Cell” Pictures

Data  Data from each fiber end is collected and plotted separately  Because the rate is low (one event every 150 seconds), data is acquired over a long period of time (>72 hours) in order to obtain a statistically significant sample

Results: Scintillator Samples  Three scintillator samples, RenDix 517p, ParDix 517p, and RenAld517p.  Results show a 20% difference in light output between scintillators made with oil from Ren Oil and those made with oil from Parol.  Pseudocumene from different suppliers appear to perform similarly.  Measurements are highly repeatable.

Results: Extrusions  We have tested several extrusion samples. Shown here are our baseline extrusion, our best extrusion made with rutile Ti0 2, and our best Anatase extrusion.  We have also included two other samples for reference:  A MINOS Strip  The duplicate “NO A Cell” painted on the inside with BC-620, an acrylic based paint loaded with TiO2(Anatase).  All measurements were performed with RenDix 517P  Initial results show we can do better that the minimum light output specification. Minimum Spec.

Upgraded Test Setup PMT M16 PMT Box Actual  Cell Lead Scintillating strip 1.2mm Clear Fiber  Increased trigger sizes. More than triple the rate, no effect on precision.  Testing apparatus is otherwise unchanged  Increased throughput of system; limited by sample preparation time, instead of trigger rate.

Extrusion tests

More Extrusion Results  Tests of recent extrusions show high and consistent light output compared to previous recipes.  Recent extrusions have also extruded well mechanically. This is CRITICAL to integrity of the detector: — the PVC is the structure

Caltech Mini Mini Tracker Minos Scintillator Trigger Minos Scintillator Trigger FRONT VIEW SIDE VIEW 16.4 cm 30 cm 60cm 40cm 150ppm ppm 250ppm N N 1” Lead “N” = Near length fibers

Actual Device  Not as photogenic, but:  Uses prototype APD  33.4m fiber (Actual length)  It works

300 ppm results

Far Light Output vs. Concentration

Measurement Summary  150 ppm  24 pe ’ s  Significant spread,  250 ppm  22 pe ’ s  Very small spread (only 2 samples)  300 ppm  35 pe ’ s  Range:  3 with ~10% spread

NO A Software at Caltech  We developed a set of light weight libraries (“SoCal”) to allow people to access NO A data and information in C++/ROOT.  SoCal consists of:  Data format for NOνA  NOvA geometry and electronics connection map  Event display package  Detector & Electronics response simulation tools  Full (and up to date) documentation.  Tools to help people write further packages.  Used by the collaboration to develop reconstruction and analysis used for TDR SoCal Caius Howcroft

Decay chain Branding Event Source Reco'ed event True Hits e/μ π p Colour = energy deposited Event Display

Caltech Reconstruction: “Subshower” Code [HZ, CH]  3D shower & Track- like feature reco.  Now the standard in MINOS  Has been applied to NO A  Preliminary use by Bob Bernstein at Fermilab shows significant signal/background separation  Needs to be carried through to a complete analysis [e.g. Patterson] “Raw Data” Sub Showers Caius Howcroft

Detector Simulation  Detector simulation code that models the light output of the scintillator, the collection of WLS fiber and the propagation to the APD, “PhotonTransporter”  Tracks individual photons and correctly deals with wavelength dependent absorption, reflection and emission coefficients.  Has been used to understand results from the Caltech test-stand and in production MC.  Accurately reproduces features of measured light collection in a cell Caius Howcroft Charged Particle Simulated Cell WLS Fibers Photon

Simulations of Light Output vs. Position

Fiber Position Results  Light Yield Simulation suggests light output decreases as fibers approach walls  Effect seen in test stand data, but magnitude smaller than predicted  Tune simulations with data to reproduce changes quantitatively

Background Studies  NO A is a search for a small signal  Understanding and correctly modeling the background is important  Work at Minnesota demonstrated the need for an overburden  This work also showed potential for Supernova detection with the overburden  Additional effort needed to determine sensitivity, and computing requirements to search for small signal events

Find the SuperNOvA 31 Leon MualemNOvA Electronics ~15min of data With typical ~10s supernova signal 1s time bins NO OVERBURDEN

Find the SuperNOvA ~15min of data With typical ~10s supernova signal 100ms time bins 1m OVERBURDEN

Software / Analysis  Created the Framework used for NOvA software development and TDR analysis  This base now being expanded to add features  Created the Subshower analysis package for MINOS, ported to NOvA framework  Showing promising results by  Needs to be carried through to a complete analysis  Created Photon propagation code  Generally useful for understanding light collection and detector performance  Validation with actual test data continues

Caltech Work on NO A  WLS Fiber R&D  Examined the effect of fiber diameter on light collection in the NO A geometry (The reduction to 0.7mm WLS Fiber saved $3 million+)  Measured light output for fibers with varying fluor concentration, ongoing optimization  Examine the effect of fiber position inside the NO A cell on light collection, ongoing input to simulation  Optical Readout System  Verify scintillator system performance using the NO A APD, original and prototype versions  Quantify results of production variability using different plastic samples, many cells and fibers  Gain experience using the new NO A APD in small scale prototype modules

Summary  NO A  Caltech has taken a leading role in NO A detector hardware R&D  Measurements done thus far at Caltech have been, and continue to be instrumental in the detector design process  We will continue to make contributions central to the detector development effort throughout the next year  We will continue to define the detector performance and identify unique capabilities, such as supernova detection  The arrival of Ryan Patterson will add considerable strength, allowing us to build on our founding roles in NO A software and analysis