# Presentation: 776269

## Borexino: ready to fill...

## Cut-away model of fully built system.

## Physics Driven

- APS Neutrino Study 2004: Borexino: This experiment, at the Gran Sasso Laboratory in Italy, is aimed at a measurement of solar neutrinos with energy spectrum sensitivity and ability to measure the flux from 7Be decays. Construction is essentially complete, but operations have been delayed. It is hoped that operations can begin in 2005. As we discuss in Recommendations, a prerequisite in physics with solar neutrinos is a determination of the 7Be neutrino flux to an accuracy of 5% or better.

- Measuring the 7Be neutrino flux will:	test if (7Be,pred)e=(0.665±0.015)(7Be,solar model)
- 	confirm LMA mechanism
- 	perhaps reveal the presence of sterile neutrinos
- 	provide an independent method to determine S34	provide next step towards determining neutrino luminosity of the sun	improve pp -flux determination from Ga experiments

## Additional Science Opportunity

- We recommend development of an experiment to make precise measurements of the low-energy neutrinos from the sun. So far, only the solar neutrinos with relatively high energy, a small fraction of the total, have been studied in detail. A precise measurement of the low-energy neutrino spectrum would test our understanding of how solar neutrinos change flavor, probe the fundamental question of whether the sun shines only through nuclear fusion, and allow us to predict how bright the sun will be tens of thousands of years from now.

- the precautions taken to enable measurement of the 7Be flux
- may allow measurement of pep (& CNO) flux as well

- Geoneutrinos and Supernovae neutrinos will also be measured concurrently as a natural complimentary use of the detector.

- Measuring the pep neutrino flux will:	be equivalent to measuring the pp flux	place excellent limits on non-standard physics	provide a complimentary measurement to a CC pp neutrino detector

## If We Find 10-17 g/g Purity...

- Rely on cosmogenic 11C being tagged.

## Challenges @ 10-16 g/g purity

- raw spectra expected at 10-16 g/g U,Th

- Best in CTF to date:
- 	238U: (3.0  0.3) x 10-16 g/g
- 	232Th: (6.5  0.9) x 10-16 g/g

- 238U:  238U()234Th()234Pa()234U()230Th()
- 	226Ra()222Rn()218Po()214Pb()214Bi()
- 		214Po()210Pb()210Bi()210Po()206Pb
- 232Th:  232Th()228Ra()228Ac()228Th()224Ra()
- 	220Rn()216Po()212Pb()212Bi()212Po()208Pb

- alpha/beta separation using tail-to-total ratio

- residual spectra ***after*** all background cuts have been made

## Detector Status

- all major hardware systems installed
- final cleaning and testing nearing completion
- needed purity of N2 achieved, CTF capable of testing purity/cleanliness of systems
- filling operations poised for execution
- detector calibration methods prepared
- data collection electronics and analysis software ready
- multiple purification methods ready to be used as needed

## Inside the Detector

**Notes:**
Here is what we see now.  Notice the addition of four pin-hole light sources (from LEDs) in the image.  This is important because...

## Detector PMT status: June  2004

**bright**

**dead**

**uncabled**

**normal**

## Time and Charge calibrations

-  ~ 1.6 *ns with 2000 PMTs*

- automatic charge calibration and allignment  of PMTs

- PMT timing and gain accomplished with laser and optical fiber system

## Borexino Calibration Strategy

- Borexino Parameters
- Energy Scales
- BetaAlphaGamma
-  Position Reconstruction
- Fiducial VolumeCorrelated EventsInternal/External/Surface
-  / Separation
-  Stability
- ChemicalOpticalMechanicalSolar Signature

## Source Insertion System

- Design based on successful CTF version.

## Slide 13

**Notes:**
Here you could explain that the source position and the LED position will be offset, and that one needs to know the angle between the two to correct for it.  To get this, one needs to know the configuration of rods within the detector (it also helps one avoid mistakes).  As in the picture, not all rod combinations can reach all locations in the detector, so a situation like that shown would be quite disturbing.  With RDP and some practice, you could show them a couple of combinations....

## 1 cm/pixel

## Source Location Method

** **

** **

** **

- Camera assembly; calibrating the image; triangulating the source (each pixel is about 1 cm at the detector center); position error distribution.

- about 2 cm position accuracy (~2% fiducial volume accuracy)

## Radioactive Sources (~10 Bq typical)

- 7Be (pure , 478 keV, 53d)*
- 32P (pure , 1709 keV, 14d)*
- 35S (pure , 167 keV, 87d)
- 69Zn (pure , 925 keV, 57m)
- 90Y (pure , 2274 keV, 64h)
- 91Y (pure , 1545 keV, 59d)
- 99Tc (pure , 293 keV, 105y)
- 113Sn (44% ek, 392 keV, 115d)*
- 137Cs (9% ek, 662 keV, 30y)
- 143Pr (pure , 931 keV, 14d)
- 210Bi (pure , 1161 keV, 5d)
- 238U (4.2 MeV )*
- 232Th (4.0 Mev )
- 40K, 14C, 85Kr, 222Rn & daughters
- etc...

- Micro-pipette

## Bi-Po life-time (air run in Borexino)

****

**D. Manuzio PhD thesis**

## discrimination power

**D. Manuzio PhD thesis**

## Fiber Optic Internal Source

- Preliminary fiber optic light source.  The quartz housing allows the UV light to propagate several centimeters before being absorbed by the pseudocumene, thus minimizing self-shielding.  The Teflon tube for Borexino will be 17 m long and used to pull sources off the vertical axis by actuating a hinge in the insertion rod.

## External Source

- External source insertion system; radial distribution of events within the inner vessel of the detector; energy distribution of events – note that the 2.6 MeV line is still visible and can be used for calibration (200 Ci Th source)

- Stability & Monte Carlo tested without contamination risk by using an external source.

## External Optic System

- IV, IB, OB optical properties tested, and reflections tested using laser beams directed through these volumes.

## Scintillator Chemical Stability

- Impurities, or change in scintillator chemistry resulting from purification, are easier to find with a gas chromatography – mass spectroscopy sampling program.  This data is critical to know *before* there are optical ramifications.

## LNGS Status

- LNGS committed to enable operation of not only Borexino, but many other experiments
- needed infrastructure improvements of laboratory for safe operation nearly completed
- legal barriers passed
- cautious and careful restart, in partnership with all concerned parties

## CTF (taken Sept 2002)

-  test systems
-  not sensitive at required Borexino purity levels

- Over two years of being locked out has taken its toll:

## Slide 25

## Need CTF for global systems check.

## Internal counts from Radial Analysis

## 5 types of backgrounds are simulated 

**Internal backgrounds (PC) **
- 238U chain in secular equilibrium;  222Rn (3.8 days);  210Pb  (22.3 y);  210Po (138.4 days);
- 232Th chain in secular equilibrium;
- 40K;  85Kr;  39Ar;
**Nylon bulk contamination: **
- 238U chain in secular equilibrium;  222Rn (3.8 days);
- 232Th chain in secular equilibrium;
- 40K;
**3. ****	****Inner Vessel Surface contamination:**
- 	 222Rn (3.8 days);  210Pb  (22.3 y);  210Po (138.4 days);
**4.****	****External backgrounds (water): **
- 238U chain in secular equilibrium;  222Rn (3.8 days);
- 232Th chain in secular equilibrium;
- 40K;  85Kr;
**5. ****	****External backgrounds (PMTs): **
- 238U chain in secular equilibrium;
- 232Th chain in secular equilibrium;
- 40K;

## 2/ndof = 1.61

- 2/ndof = 1.61

- Energy fit – example

- Huge number of parameters (>25): beyond capability of CTF to distinguish

## Slide 30

## Operations Schedule

- Physics start near end of 2006; 3-5 yrs minimum.

| 2006 Tasks | # of weeks |
| --- | --- |
| Water Fill SSS | 12 |
| SSS Water Data Run | 10 |
| Fill Water Tank | 8 |
| Water Tank Water Data Run | 4 |
| Scintillator Fill | 24 |

## Slide 32

##  discrimination results

-  discrimination results

| 
Z | SVM |  |  |  |
| --- | --- | --- | --- | --- |
|  |  |  |  |  |
|  | 5 | 1 | 95 | 99 |
| 0 | 98.4 | 93.1 | 1.2 | 5.6 |
| 50 | 98.3 | 94.1 | 1.1 | 7.5 |
| 150 | 98.3 | 89.9 | 1.4 | 8.2 |
| 250 | 98.5 | 87.3 | 1.7 | 9.4 |
| 400 | 92.2 | 68.9 | 5.5 | 23.5 |

- CTF data: 10  c/d in 4 t, yielding about 200 c/d in Borexino
-  With this (optimistic)  separation, we are almost at the required purity level (with 98%  4 counts/day expected)

## Anti-neutrino from Earth: Spectrum

- A 10 TW geo-reactor can be identified at the level of 2 in 1 years

**10 TW geo-reactor**

## Anti-neutrinos in KamLAND for comparison