# Presentation: 787155

## MiniBooNE – “The Last Fun HEP Experiment”

*Eric Prebys*
- FNAL Beams Division/MiniBooNE

## MiniBooNE Collaboration

- ~65 Physicists

## Trivia Quiz

- The official designation of MiniBooNE is Fermilab E-898...
- What was Fermilab E1?
- What Nobel Laureate was on the proposal?
- How does it relate to MiniBooNE?

## Outline

- Introduction:
- What are neutrinos?
- How do we study them?
- What is the problem?
- Where does MiniBooNE fit in?
- The MiniBooNE experiment:
- Overview
- Detector
- Target
- Beamline
- MiniBooNE Operation
- Details of MiniBooNE cycles
- Rate issues
- Timeline issues
- Running Modes

## What is a Neutrino?

- Electron Energy

- Expected monoenergetic electrons

- Observed electron spectrum

- In “beta decay”, one element changes to another when the nucleus emits an electron (or positron)

- It was even postulated that maybe beta decay violated conservation of energy!

- In 1930, Wolfgang Pauli suggested a “desperate remedy”, in which an “invisible” particle was carrying away  the missing energy. He called this particle a “neutron”.

- Enrico Fermi changed the name to “neutrino” in 1933, and it became an integral part of his weak decay theory.
- The theory was extremely successful, but the neutrino was not directly observed until 1956, by Fred Reines *et al.*

## Neutrinos in the Standard Model

- Each Generation lepton has an associated neutrino

- The weak interaction causes a charged lepton to “flip” to a neutrino and vice versa

- The weak interaction conserves “lepton number”

## Problems Studying Neutrinos

- Neutrinos interact only weakly.  A 1 GeV neutrino (a la MiniBooNE) could easily pass through a block of solid lead stretching *from the Earth to the sun!!!  *Typical neutrinos from nuclear reactions could go 1000 times further.
- Even a huge detector will only detect a tiny, tiny, tiny, tiny, tiny fraction of the neutrinos passing through it.
**No neutrino has ever been produced and detected in a particular interaction****.**
- Two ways to study neutrinos:
- Detect all the particles from a particular reaction and attribute anything “missing” to a neutrino. (LEP, CDF, etc...)
- Make a hell of a lot of neutrinos and detect a very, very tiny fraction of them. (Solar Neutrinos, Reactor Experiments, **BooNE**)

## Sources of a Hell of a Lot of Neutrinos

- The sun:
- Mechanism: nuclear reactions
- Pros: free
- Cons: only electron neutrinos, low energy, exact flux hard to calculate, can’t turn it on and off.
- Atmosphere:
- Mechanism: Cosmic rays make pions, which decay to muons, electrons, and neutrinos.
- Pros: free, muon and electron neutrinos, higher energy than solar neutrinos, flux easier to calculate.
- Cons: flux fairly low, can’t turn it on and off.
- Nuclear Reactors:
- Mechanism: nuclear reactions.
- Pros: “free”, they do go on and off.
- Cons: only electron neutrinos, low energy, little control of on and off cycles.
- Accelerators:
- Mechanism: beam dumps -> particle decays + shielding -> neutrinos
- Pros: Can get all flavors of neutrinos, higher energy, can control source.
- Cons: NOT free.

- Different experiments probe different ranges of

- Path length

- Energy

## Problems with Neutrinos

- We know from the kinematics of decays that the mass of the neutrino is very small (consistent with zero in these measurements).
- In the model, the mass of the neutrino is defined as exactly zero.
- The “Problems”:
- “Solar Neutrino Problem”: It was discovered (~1968) that there didn’t appear to be enough electron neutrinos coming from the sun.
- “Atmospheric Neutrino Problem”: It was discovered (~1987) there weren’t enough muon neutrinos coming from the atmosphere.
**Possible Solution: Enough neutrinos being created, but they’re oscillating (or decaying) to something else.****  **

***This would mean neutrinos have mass!!***

## Questions to be Answered

- What are neutrino masses?
- What are the details of the mixing?
- Are neutrinos the dark matter?
- Does                    (“Majorana Neutrinos”) ?
- Is the physics of neutrinos and antineutrinos the same (CP or CPT violation)?

## State of Experimental Observations

- Many experiments have confirmed the “neutrino problems”.
- Data from SuperKamiokande supports the model that atmospheric muon neutrinos oscillate to tau neutrinos.
- Data from SNO supports the hypothesis that solar electron neutrinos oscillate to muon and or tau neutrinos.
- The LSND experiment at Los Alamos claims to have seen muon antineutrinos oscillate to electron antineutrinos -> Not really compatible with the other results in within a simple model.

## Where does MiniBooNE fit in?

- So far, the LSND result is the only example of a specific neutrino “appearance”.
- The theoretical picture is simpler without it.
- It is as yet unconfirmed.
**MiniBooNE aims to definitively confirm or refute this result.**

## MiniBooNE Sensitivity

- Difference in the *square* of the mass between e and 

- “Strength” of mixing

## Producing Neutrinos for MiniBooNE

- Proton beam

- Mostly pions

- Berylium Target

- Mostly below our detection threshold

- We will look for these to oscillate to e

- Select positive pions with neutrino horn.

## Neutrino Horn – “Focusing” Neutrinos 

- Can’t focus neutrinos themselves, but they will go more or less where the parent particles go.

- Target

- Coaxial “horn” will focus particles of a particular sign in both planes

- p

- We select + -> 

## Neutrino Horn – Cont’d

-  Horn will pulse with 170 kA 150 usec pulse!
-  Horn heating limits the average rep rate to 5 Hz.
- Horn fatigue is an issue.
- BooNE Horn has been tested to 10 million pulses.
- Under nominal MiniBooNE running conditions, it will pulse about 100 million times per year.

## MiniBooNE Secondary “Beamline”

- 25m

- 25m

- Detector

- “Teletubby Hill”

- Counting House

- 50m Muon absorber

- removable25m Muon absorber

- Target vault

- Proton Beam

- Decay region

- NOT to scale!!!!!!

- 500 m

## The MiniBooNE Detector

- Oscillation!!!

- Our beam will produce primarily muon neutrinos at high energy

- This is what we’re looking for

- 807 tons of mineral oil

- 1280 PMT’s

## Identifying Particles

- Oscillation Signature

- Of course it’s a bit more complicated than that...

## The Ghastly Economics of MiniBooNE

- On average, every proton on target will produce several neutrinos.
- Very few of these will interact in the detector.
- We will only see 1 neutrino event for every 2.5E14 protons on target!!!!
-  If we run at the full desired intensity:
- 5E12 protons/batch
- 5 batches/second
- 			  1 event every 10 seconds!!

## The Road to MiniBooNE ($1D Event Cycle)

**H****-**

**I****-**

**Preac**25 keV 750 keV

- Old 200 MHz Linac750 keV 116 MeV

- New 800 MHz Linac116 MeV 400 MeV

- Debuncher

- ORBUMP Injection

- Booster (20000 turns) 400 MeV 8 GeV

- Main Injector

- MiniBooNE Horn

- Switch Magnet (E:MBEX)

## MiniBooNE Beamline

## MiniBooNE Switch Magnet (E:MBEX)

-  MiniBooNE acceleration and extraction are handled exactly as if they were going to the main injector.
- Beam is transported down the MI-8 line.
-  The MiniBooNE switch magnet is located where the MI-8 line enters the main injector tunnel.
-  On $1D cycles, the switch magnet (E:MBEX) will pulse to about 1470 Amps, which will steer the beam to the MiniBooNE beam line MI-12.

## MiniBooNE Beamline Monitoring

- = Multiwire

- Present Location of beam dump

-  BPM’s and BLM’s located throughout beam line, *except in jack pipe.*
- Resistive Wall Monitor will measure beam structure near target
- 90 Degree Monitor will verify beam on target.

## MiniBooNE Beamline Control and Monitoring

- MiniBooNE beamline parameters on E25.
- Eventually we’ll control with autotune program.

- Multiwires on E26

- BPMs/BLMs on E27

## Target Monitoring (90 Degree Monitor)

-  Difficult to monitor target because of high radiation.
-  Will detect particles coming off at 90 degrees through a hole in the shielding.
- Even outside the steel, still a very high background of neutrons.
- Use a Cerenkov-based, neutron-blind detector.
- Will also provide beam timing.

- Proton Beam

## Commissioning Plan 

- Rig dump at position shown (Done).
- Transport beam to dump (Done).
- Tune beam and minimize losses (almost done).
- Rig out dump and transport beam to Multiwire at target position and down decay pipe.
- Install horn and target, remove, reinstall to prove we can handle it when it’s radioactive (“Hot Horn Handling”).
**Install horn and run real beam to MiniBooNE (approx. mid-June).**

## First Beam to Dump: 4/29/02 4:03AM

## Some Running Considerations

- Recall, MiniBooNE will only see one neutrino event every 10 seconds at maximum intensity.
- The detector will read out every beam spill (5 Hz) plus various other triggers.
- This has already been demonstrated.
*It will take analysis to tell whether the beam is there at all!!*
- -> No detector shakedown time!  We want all the beam as soon as possible.
- And just how much beam is that....

## The Numbers

- Run II max 5E12 @ .7 Hz = 1.2E16 pph.
- Historical High (fixed target, no buildings): 3E16 pph.
- MiniBooNE wants 5E12 @ 5 Hz = 1E17 pph.
- MiniBoonE+RunII = 1.1E17 pph.
*This will be hard!!!*
- Physical Limits of Booster
- Above Ground Radiation
- Below Ground Radiation
- MiniBooNE beamline radiation (???)

## Pulsed element limits

- Linac chopper: 15 Hz
- ORBUMP Magnets: 7.5 Hz (lots of work to go to 15Hz).  No spares!!
- Booster RF: 7.5 Hz (Maybe go to 15 if we use existing cooling lines). No spare PS.
- BEXBMP: 15 Hz
- Extraction kickers: 15 Hz
- MP02 extraction septum: 2.5 Hz (New PS -> ~4 Hz, New magnet + PS -> 7.5Hz, + more cables -> 15 Hz.

## Pulsed element limits

- Linac chopper: 15 Hz
- ORBUMP Magnets: 7.5 Hz (lots of work to go to 15Hz).  No spares!!
- Booster RF: 7.5 Hz (Maybe go to 15 if we use existing cooling lines). No spare PS.
- BEXBMP: 15 Hz
- Extraction kickers: 15 Hz
- MP02 extraction septum: 2.5 Hz (New PS -> ~4 Hz, New magnet + PS -> 7.5Hz, + more cables -> 15 Hz.

## Radiation Issues

- Radiation Limitations
- Above ground (want to avoid towers being radiation areas and keep office space as “Unlimited Occupancy”).
- Shielding added in Booster towers.
- Reclassify some work areas.
- Reduce beam losses
- Below ground (must avoid making booster elements too hot to handle).
- Reduce beam losses

## Best Performance + Shielding + BooNE Intensities

## Below Ground Radiation

- Below Ground Radiation does not have hard limits.
- Nevertheless, we would like to prevent element damage (occurs ???).
- We would like to reduce activation, particularly to elements that frequently need service, RF cavities in particular.
- Here’s where radiation is now:

## Collimator System

## Ramped Correctors

- While the main lattice magnets in the booster ramp with *B**** p*, the orbit correctors have historically remained constant  beam moves around during cycle.
- We have put in 24 ramped control cards in each plane to actively control the beam throughout the cycle.
- The deviation of the booster orbit from an ideal orbit is measured at a number of discrete time breaks; this is used to calculate an optimum set of corrector currents to minimize the RMS of this deviation, taking into account the limitations on maximum current and current slewing.
- These optimum settings are then loaded into individual ramp modules to provide a time dependent current to maintain the booster at the desired orbit.

## Ramped Corrector Status

- Program is working.
- Added more user friendly “steering” interface.
- Reduced number of time breaks to speed up calculation time.
- Working on misc. operational improvements.
- Will become important as we start to use the collimators.

## Timeline Issues

**At all times, MiniBooNE will want as many cycles as possible without reaching radiation or physical limits.**
- Some Booster elements require two “prepulses” ($12) prior to instantaneous 15 Hz operation.
- In order to minimize average booster rep rate, we would like to have the prepulses followed by all appropriate event.
- Easy example: Stacking
- $12,$12,($17),$14,$1D,$1D,$1D.......
- Unfortunately, this is much more complicated during shot setup or studies which are occurring up to half the time.
- In present timeline generator (TLG), $1D’s would have to be put in by hand to all the modules in the timeline –> NOT PRACTICAL.
- Idea proposed by Bob Webber is that each TLG module can have a MiniBooNE “trailer hitch”, and an automatic supervisor application would distribute $1D’s throughout the cycle subject to radiation and average rep rate limitations.

## Schedule

- MiniBooNE will begin taking first physics data in mid-June (with new MP02 power supply).
- We hope to be able to confirm or refute the LSND result in about 2 years of running.
- What happens after that depends on what we see.
- Switch horn current to run with anti-neutrinos?
- Build a second detector to probe L/E (MiniBooNE->BooNE)?
- The operation of MiniBooNE will be a challenge for proton source, both in peak performance and level of consistency.

## Trivia Answers

- The official designation of MiniBooNE is Fermilab E-898...
- What was Fermilab E-1?
- A measurement of  charged and neutral interaction cross-sections.
- What Nobel Laureate was on the proposal?
- Carlo Rubbia - later to win Nobel prize and become director of CERN.
- How does it relate to MiniBooNE?
- 30 years later, neutrinos are still interesting and mysterious.
- Ray Stefanski is/was on both experiments.