NuMI

MINOS

The MINOS Far Detector

Cosmic Rays and their neutrinos are being collected now.

How does this work, and of what use is this data?

Alec Habig, Univ. of Minnesota Duluth, for the MINOS collaboration

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 2

The MINOS Experiment

• Main Injector Neutrino Oscillation Search– Will utilize NuMI beam from

Fermilab

• Front-to-back oscillation study

– Produce well-studied beam

– Measure spectrum just after production with “Near Detector”

– Measure again 735 km later with “Far Detector”

• Beam goes from Fermilab to the Soudan Mine Underground Lab735 km

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 3

The Far Detector

• Steel/Scintillator sampling calorimeter– 5.4 kt, 8m diameter, 31m long– 486 layers, each made of:

• 1” steel• 1 cm plastic scintillator

– Magnetized to ~1.5 T

• Design goals – e// discrimination– Good energy resolution

• For both and showers

– Good timing, both hit-to-hit and absolute• For particle direction and

synching with Fermilab beam

½ of the Far Detector

To Fermilab

15m

8m

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 4

Far Detector Progress

• Construction began August 2001

• Now up to about plane #225– Almost halfway done!– First half complete in

July when it will be magnetized

• Taking Cosmic Ray data as it is built– Each plane

independently instrumented

Plane #200, May 3, 2002

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 5

Particle Detection

• 4.1 cm x 8m scint strips bundled into “modules”– Light channeled out via 2-

ended fiber

• Each plane’s strips are 90o from the last– “U” and “V” views

• 17 GeV MC shown below from side, in U,V

28

28

2828

2020

2020

From FNAL

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 6

Multiplexing

• Light detected by 16 pixel PMTs

• 8 fibers per pixel, ganged together with:– Maximal physical strip

separation– Minimal in-PMT cross-

talk

M16 PMT

16 mm

Fiber Layout

One of 3 Ham. M16PMTs in this “Mux Box”

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 7

Front End Electronics

• Fibers from each strip end are multiplexed onto PMT pixels• Signals amplified, shaped, and tracked+held by “VA” chips

– Calibration charge can also be injected in the same place as PMT charge for functionality check and calibration of full electronics path

• Timing information sent upstream from this “Front End” rack

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 8

Data Gathering

• VME “Master” crate– VA Readout Controllers

“VARC”s• Charge from PMTs digitized

by 14-bit ADCs• Time stamped to 1.6ns by

internal clock

– 2/6 or 2/36 pre-trigger applied– Hits given absolute GPS time

• Data read out over PVIC bus to computer room– 4/5 plane software trigger

applied, hits time ordered– Data formatted in ROOT

1 of 16 VME cratesDigitizes 72 mux boxesEach w/3 16-pixel PMTs

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 9

De-multiplexing

• Scintillator strip ends are multiplexed 8-1 per electronics channel

• How to figure out which strip a particle really went through?

• Matching hits on both ends of a strip helps in the simplest track case

• For multiple hits on a plane and showers:– All the different possible “hypotheses” of which strip was

really hit tested against the possible real physics– Best fitting hypotheses saved

• Reconstructing close multiple muons very difficult!

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 10

A Cosmic Ray De-multiplexed

• Success rate for Cosmic Rays:– 94% of hits correctly associated with their strips– 97% of CR events successfully sorted out

CR before De-multiplexing CR after De-multiplexing

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 11

Light Injection

• Calibration using controlled light:– LEDs illuminate 8-10 calibration fiber ends each– Fibers carry light from LED to shine on ends of scint strip fibers

• Varying light levels used to map out detector and phototube response

• Regular pulsing at a constant light level during normal operations – Tracks changing detector response– Flags problems with optical path

Light from calibrationfibers illuminating ends of fibers from the scintillatorwhere they are bundled

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 12

Cosmic Rays

CR- light output with expectations~10 pe at mid-strip (sum of both ends)

• As planes are added to the detector, they contribute to the data acquisition

• Currently taking Cosmic Ray data– CR rate: 1000 /strip/month,

2% stop in detector

• Excellent “beam” for detector commissioning– Real particle data provide end-

to-end test of all hardware, software systems

• Good calibration source– Geometry, gain, timing,

reconstruction software

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 13

CR Calibrations

• Physical plane locations are surveyed as the planes are raised– CR draw nice straight lines– Residuals to the fits are not bad with nominal plane

geometry, excellent with survey-corrected data

• Timing calibrations– CR are nice straight lines moving at =1– Use this physics to find and fit absolute timing offsets

Need t0 fit plot

Timing offsets (ns) vs. channel.Different delays in different electronics paths are clearly seen, as is the few (2.6) nanosecond resolution

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 14

Initial Searches

• Atmospheric are present in the data– Contained vertex search

being refined– Up-going search

underway as part of CR timing calibrations

• Reconstruct timing of tracks– Down-going CR’s have

=1– Up-going -induced

have =-1

An up-!

Neutrino 2002, May 25-30, 2002, Munich

Alec Habig

NuMI

MINOS

Page 15

Summary

First ! An up-going seen on the evening of March 22, 2002 – MINOS works!

• The MINOS Far Detector construction is nearing the ½ way point

• Data being taken as the detector grows is used to validate and calibrate both hardware and software

• Will be ready for beam– Plus atmospheric work

can be done with magnetic field!• / separation

The presenter gratefully acknowledges support for this poster from the National Science Foundation via its RUI grant #0098579