How to Build a Neutrino Oscillations Detector

-Why MINOS is like it is!

Alfons Weber

March 2005

March 2005 A. Weber

MINOS Experiment 2

Neutrino Oscillations• MINOS is a long baseline Neutrino Oscillation

Experiment– What do we want to measure?

– We want to see, how one type of Neutrino transforms itself into another.

– There is a characteristic pattern, if this is transformation is due to “neutrino mass eigenstates”

• Simplified two neutrino scenario:

22 2 1.27

( ) 1 sin (2 )sinm L

PE

1

2

cos sin

sin cos

or 1 2,

March 2005 A. Weber

MINOS Experiment 3

March 2005 A. Weber

MINOS Experiment 4

NuMI & The Main Injector Fermilab Main Injector:

120 GeV protons 2.5 x 1013 protons/pulse 1.9 sec rep rate (~8 sec spill) 0.25 MW

NuMI Beam:

Graphite target Two magnetic horns 675 m. vac. decay pipe hadron absorber designed for 4 x 1013 ppp

Beam Monitoring:

muon detectors hadron detectors + Near Detector !

March 2005 A. Weber

MINOS Experiment 5

NuMI Beam Layout

March 2005 A. Weber

MINOS Experiment 6

120 GeV primary Main Injector beamTarget readily movable in beam direction2-horn beam adjusts for variable energy ranges675 meter decay pipe for decay

Neutrino Production

March 2005 A. Weber

MINOS Experiment 7

MINOS Physics Reach

νµ CC Events/year(with no oscillations)

Low Medium High 1,600 4300 9250

Nominal Beam Configurations Intense beam from FNAL- initially 2.5 x 1020 p.o.t./year, (being commisioned now !!)

Beam spectra: M. Messier

March 2005 A. Weber

MINOS Experiment 8

• Charge current– electron

– muon

– tau

– Can measure neutrino energy

• Neutral Current– electron

– muon

– tau

μ ν μ

hadrons

5 m

ν μ

hadrons

ν μ

1.5 m

Neutrino Interactions

March 2005 A. Weber

MINOS Experiment 9

Oscillation Pattern2

2 2 1.27( ) 1 sin (2 )sin

m LP

E

2 3 23 10m eV

735 kmL

No Effect!

measures m2

Smeared by resolution

P ~ 1/2

2 Em

L

March 2005 A. Weber

MINOS Experiment 10

MINOS Analysis• Select νμ charge current events

and reconstruct neutrino energy

Energy resolution:

Compare energy spectrum in near and far detector

Measure Δm2 and sin22θ

• Look for appearance of νe

beam & NC contamination

hEEE

range, B field calorimetric

EEE

pp

hh /%60/

%10/

Δm2

sin22θ

March 2005 A. Weber

MINOS Experiment 11

Where should the Experiment be?

• Δm2= 0.002-0.003 eV2 (from SK)• In oscillation Minimum

L/E = 400 - 800 km / GeV• Larger distance shorter distance• High energy low energy• Flux ~ 1/L2

• Cross section ~ E • Event size ~ E

March 2005 A. Weber

MINOS Experiment 12

• NuMI beam travels 735 km to Soudan (MN)

• Sagitta:10 km

• 1 km wide at destination

The MINOS Experiment

March 2005 A. Weber

MINOS Experiment 13

March 2005 A. Weber

MINOS Experiment 14

Detector

• Design requirements– High Mass

– High segmentation– Affordable

March 2005 A. Weber

MINOS Experiment 15

MINOS Detectors• There are 3 MINOS Detectors

– Near Detector @ FNAL (ND)

– Far Detector @ Soudan (FD)

– Calibration Detector @ CERN (CalDet)

• Magnetised steel scintillator tracking calorimeter– Alternating planes of steel and scintillator strips

5.4 kton

12 ton0.9 kton

March 2005 A. Weber

MINOS Experiment 16

Soudan Underground Laboratory

• former iron mine, now a state park, – home of: Soudan-1 & 2 , CDMS-II , and MINOS expts

March 2005 A. Weber

MINOS Experiment 17

MINOS Construction Challenge

March 2005 A. Weber

MINOS Experiment 18

Bottom steel plane layer

Top steel plane layerScintillator planeOrientations alternate

90o in successive planes

2-m wide, 0.5-inch thicksteel plates

MINOS Plane

March 2005 A. Weber

MINOS Experiment 19

Far Detector• In old iron mine• Was already there

– Soudan 1 & 2

• Right distance from FNAL

March 2005 A. Weber

MINOS Experiment 20

8 m

Scintillator Module

WL

S Fi

bers

WL

S Fi

bers

Optical Connector

Optical Connector

Optical Connector

Optical Connector

Cle

ar F

iber

Rib

bon

Cab

le (

2-6

m)

MultiplexBox

MultiplexBox

PMTs

Con

nect

ion

to

elec

tron

ics

Con

nect

ion

to

elec

tron

ics

MINOS Scintillator Module

• 4-8m scintillator modules

• 24-28 strips

• double sided readout

• multi anode PMTs (16/64)

March 2005 A. Weber

MINOS Experiment 21

PMT• Light is detected by

multi-anode PMTs– 230x 64-pixel in ND

– 1500x 16-pixel in FD

• pixel to pixel variations

March 2005 A. Weber

MINOS Experiment 22

FD Front End Electronics • MINOS developed an ASIC chip for PMT readout

– 32 channels

– shaping

– amplification

– sample & hold

– output driver to ADC

• Excellent product – fast shaping 500 nsec

– noise < 2 fC

– linear> 20 pC

– 6 ASICs multiplexed onto 1 ADC

March 2005 A. Weber

MINOS Experiment 23

Signal Amplification

March 2005 A. Weber

MINOS Experiment 24

Output of Pre-amplifier

March 2005 A. Weber

MINOS Experiment 25

Signal Digitisation

March 2005 A. Weber

MINOS Experiment 26

DAQ System• Trigger-less DAQ system

– ASIC close to PMT

– ADC in VME crate

– fast PVIC-bus to PC trigger farm

– search for hits correlated in space and time

1

DCPDCP

TP0

TP0TP

N

TPN TP

1

TP1

VARC0

VARC0VARC

1

VARC1VARC

2

VARC2 VARC

0

VARC0VARC

1

VARC1

ROPROP

0

VARC2

VARC2

VME

VFBVFB

2 1 0

DAQLAN

serial

Ether.ROP

ROP

15

TRCTRC

VME

VFBVFB

PVIC

DAQLAN

serial

Ether.

3

40 Mbytes/sPVIC Bus

10-100 Kbytes/s

DAQLAN

VME Readout Crates

0 Optical PVIC Bus

2.5 MB/s

To Persistent StoreTo Dispatcher

DAQLAN

TimingCentral

unitGPS

antenna

TimingPC

TimingPC

Timing System

Timestamp Clock1 sec GPS ticks

DAQLAN

3

TRCTRC

PVIC

2 1 02 1 02 1 0

BRP

BRP

BRP

BRP

PMTsHVHV HV HV

RCRC

2

TriggerProcessors

Branch Readout

Processors

Front End Electronics

• Timing System– Absolute time from GPS

(tabs= 200 nsec)

– optical distribute along large detector (trel= 4 nsec)

March 2005 A. Weber

MINOS Experiment 27

Near Detector Event

MINOS Preliminary

Etrack approx. 1.5 GeV

Low-energy track from fiducial region

March 2005 A. Weber

MINOS Experiment 28

Additional Near Detector Events

MINOS Preliminary

Etrack approx. 3.1 GeV

Medium energy track from near peak in “pseudo-medium” beam

March 2005 A. Weber

MINOS Experiment 29

Additional Near Detector Events

MINOS Preliminary

One “snarl” (beam pulse) in near detector, showing multiple events.