The Scintillating Fiber Tracker and Muon Trigger at

The Scintillating Fiber Tracker and Muon Trigger at DZero Maris Abolins For the D 0 Collaboration 7/13/01 Maris Abolins-HEP 2001, Budapest

Upgraded D 0 Detector 7/13/01 Maris Abolins-HEP 2001, Budapest 2

The DØ Scintillating Fiber Tracker z 8 nested cylinders y r = 20 ® 51 cm z On each cylinder scintillating fibers y 2. 5 m or 1. 7 m, long y 835 um diameter z Fibers arranged into y 1 axial doublet y 1 stereo (u or v) Constant pitch » 3 o z Total channel count >77 K z Clear fiber, 7 - 11 m long, brings signal to VLPCs 7/13/01 Maris Abolins-HEP 2001, Budapest 3

DØ Scintillating Fiber Tracker: Operational Principles Scintillating Fiber Mirror z. A charged particle crosses a scintillating fiber, where it causes a ‘blink’ of light. z. The light is transported via optical fiber over a distance of 8 -11 meters to a device called a VLPC which converts light into electricity. z. VLPC is a solid state device that operates at cryogenic temperatures. z. A ‘cassette’ of VLPC devices Photodetector Cassette contains 1024 channels and is housed in a cryostat, which carefully regulates the operating temperature. Optical Connector Waveguide Fiber Electrical Signal Out Cryostat 7/13/01 Maris Abolins-HEP 2001, Budapest 4

DØ Fiber Tracker Eight cylinders covered with scintillating fiber are read out with a novel light detector (VLPCs). VLPCs 7/13/01 Maris Abolins-HEP 2001, Budapest See the Display!5

VLPC History In 1987, a paper was published by Rockwell detailing the performance of Solid State Photo. Multipliers (SSPMs). These solid state devices detected both visible and infrared light. Infrared detection technology is regulated under international treaty so Fermilab proposed a device which maintained the visible light response, but reduced the infrared response. This device is called a Visible Light Photon Counter (VLPC). With the successful demonstration of VLPC technology, the High. Resolution Scintillating Fiber Tracking Experiment (Hi. STE) proposal detailed using scintillating fiber technology combined with VLPCs to track particles from high energy particle collisions. There have been six models of Hi. STE chips, with Hi. STE-VI being used in the DØ experiment. 7/13/01 Maris Abolins-HEP 2001, Budapest 6

VLPC Operational Principles Gain Intrinsic Region z. Photon is converted in the intrinsic region, creating an electron-hole pair. z. Hole drifts into the drift region, where it knocks an electron out from an atom. z. Electron accelerates back through gain region, knocking electrons from atoms as it goes. z. Spacer region and substrate are for mechanical support and field shaping. Drift Region Substrate Spacer Region • e • h Photon • + Top Contact (+) E field z. Thus each photon generates a pulse of many electrons. Gains of × 20, 000 – 60, 000 are achievable. • n n gio e gio Bottom R e R in ift r Ga Contact (-) D D+ flow Undoped Silicon Doped Silicon Layer (Blocking) Layer 7/13/01 Maris Abolins-HEP 2001, Budapest 7

Hi. STE VI z. Solid state photon detectors z. Operate at a few degrees Kelvin (~ -450° F) z. Bias voltage 6 -8 Volts z. Detect single photons z. Can work in a high rate environment z. Quantum efficiency for visible light ~80% z. High gain ~50 000 electrons per converted photon z. Low gain dispersion z. Highly suppressed infrared sensitivity 7/13/01 0 1 2 3 Maris Abolins-HEP 2001, Budapest Visible 8

HISTE VI Wafer 7. 62 cm (3”) Each wafer is grown via vapor phase epitaxy and then masked for the desired Maris Abolins-HEP 2001, configuration. 7/13/01 Budapest VLPC Chip 0. 30 cm (0. 12”) Each VLPC pixel is a 1 mm diameter detector, well suited for use in scintillating fiber applications. 9

Gain 1400 20 000 Frequency 1200 60 000 Gains (in thousands) Range from 20 000 to 60 000 1000 800 600 400 200 0 0 10 20 30 40 50 60 70 80 Gain (in Thousands) Gain dispersion of the pixels within one chip About 1. 5 % 1200 Frequency 1000 800 600 1. 5 % 400 200 0 0 0. 5 1 1. 5 2 2. 5 3 3. 5 4 4. 5 5 Gain RMSMaris (%) Abolins-HEP 2001, 7/13/01 Budapest 10

Quantum Efficiency and Gain Behavior z. QE and gain are a function of voltage z. Relative gain is highly correlated 63. 1 60 40 20 86. 0 25. 4 32. 6 50 30 83. 6 49. 6 70 16. 9 Absolute QE(%) 80 78. 4 90 72. 6 100 81. 7 110 10 0 5. 6 6. 0 6. 4 6. 8 7. 2 7. 6 Voltage 7/13/01 Maris Abolins-HEP 2001, Budapest 11

Linearity at 0 MHz Background Deviation from Linearity of VLPC, Representative Chips Response of High Gain VLPC 1000 Normalization Point 20 Deviation (%) 0 1. E+00 -20 -40 1. E+01 Measurement Artifact 1. E+02 1. E+03 1. E+04 Gain ~30 000 Gain ~50 000 -60 1. E+05 Integrated Charge (Arbitrary Units) 40 -80 measured linear reference 100 10 1 0. 1 1. E+00 1. E+01 1. E+02 1. E+03 1. E+04 1. E+05 Equivalent Photoelectrons = QE(for one pe) * photons -100 Equivalent Photoelectrons = QE(for one pe) * photons z VLPC’s are linear to <10% for Equivalent PE ~600 (~750 photons). z Increasing non-linearity with increasing gain. 7/13/01 Maris Abolins-HEP 2001, Budapest 12

Connected Fibers - Stereo Board Only Lack of final electronics has forced us to read out a portion of the CFT with prototype electronics 7/13/01 Maris Abolins-HEP 2001, Budapest 13

Event Displays (magnet off) Instrumented Region 7/13/01 Maris Abolins-HEP 2001, Budapest 14

Fiber Occupancy (Min Bias) 7/13/01 Maris Abolins-HEP 2001, Budapest 15

Summary z Tracking hardware installed and working z Electronics y 25% on hand now y The remainder scheduled to arrive within ~1 month y Will need another ~1 month for installation and checkout 7/13/01 Maris Abolins-HEP 2001, Budapest 16

DØ Muon System Muons provide a signature of many interesting physics events. Muons penetrate dense material for long distances. Thus muon detectors are outside the large amount of metal that makes the rest of the detector. The muon system consists of many different detector technologies, and is the physically largest system. 7/13/01 Maris Abolins-HEP 2001, Budapest 17

Muon scintillators 7/13/01 Maris Abolins-HEP 2001, Budapest 18

Muon drift tubes 7/13/01 Maris Abolins-HEP 2001, Budapest 19

Mu Trigger schematic 7/13/01 Maris Abolins-HEP 2001, Budapest 20

Muon front ends 7/13/01 Maris Abolins-HEP 2001, Budapest 21

SLIC 7/13/01 Maris Abolins-HEP 2001, Budapest 22

SLIC Outputs 7/13/01 Maris Abolins-HEP 2001, Budapest 23

Alpha outputs 7/13/01 Maris Abolins-HEP 2001, Budapest 24

Software Projects 7/13/01 Maris Abolins-HEP 2001, Budapest 25

L 1 MU Status z Work in progress y Developing L 1 MU examine - highest priority y Tracking down Muon FE - L 1 MU interface problems y Understanding muon octant trigger rates y Verifying that the Muon FE systems are timed in to the correct BC y Understanding and fixing a number of hardware bugs y Completing software connection to COOR y Increasing sophistication of triggers y Continuing development of trigger simulation 7/13/01 Maris Abolins-HEP 2001, Budapest 26

L 1 MU Trigger Rates @ 4 e 30 7/13/01 Maris Abolins-HEP 2001, Budapest 27

Summary z Much of detector hardware installed and working z Most trigger electronics installed and undergoing tests z Most of software elements are in place z Monitoring software is a high priority 7/13/01 Maris Abolins-HEP 2001, Budapest 28