# Presentation: 090133

## Stellar Neutrino Studies at the Spallation Neutron Source(Oak Ridge)

**S**tellar **N**eutrino **S**tudies at the **S****pallation** **N**eutron **S**ource(Oak Ridge)

- (SNS)2

**NuFact 03 - June 10****th**

- Or study of neutrino nucleus cross sections at **veeery** low energy

## Pre supernovae

-  **Evolutionary stages of a 25 MSUN star:  **
-         **Stage          Temperature (K)  Duration of stage**
-     Hydrogen burning      4 x 107               7 x 106 years
-     Helium burning          2 x 108               5 x 105years
-     Carbon burning          6 x 108                  600 years
-     Neon burning           1.2 x 109                    1 year
-     Oxygen burning        1.5 x 109                 6 months
-     Silicon burning         2.7 x 109                   1 day
-     Core collapse           5.4 x 109                  1/4 second

## Supernovae

-  **Recorded explosions visible to naked eye:**
**      ****Year (A.D.)                      Where observed                         Brightness**
-             185                                      Chinese                         Brighter than Venus
-             369                                      Chinese                    Brighter than Mars or Jupiter
-           1006           China, Japan, Korea, Europe, Arabia         Brighter than Venus
-           1054                          China, SW India, Arabia               Brighter than Venus
-           1572                                        Tycho                         Nearly as bright as Venus
-           1604                                        Kepler                            Brighter than Jupiter
-           1987                                Ian Shelton (Chile)

## Explosion

**Collapse and re-bound(1-4) creates a shock wave(5) propagating outward from center of core(6) , meeting in falling outer core material****	**
**Shock stalls due to neutrino escape & nuclear dissociation**
**Deleptonisation of the core creates intensive neutrino flux (99% of energy) **
**Neutrino interactions behind the shock reheat the shock and drive it outwards(7)**
**Measuring ****56****Fe(********e ****,e****- ****) ****56****Co  provides valuable data to guide shock formation models.**
**Other cross sections, ****28****Si, should also play an important role.**

**5**

## Energy in supernovae

**Total energy – 10****53**** erg**

**98% of the energy is emitted by neutrinos !!!!**

## -Process Nucleosynthesis in Supernovae

** ****“******** ****process nucleosynthesis” could be an ****	****important new dramatically altering the r-process (push through waiting nuclei)**
-  **“******** ****process nucleosynthesis” can produce**
**   ****rare isotopes  - ****180****Ta, ****138****La, ****19****F, ****10,11****B **
** ****These isotopes cannot be produced at other**
**  ****sites and thus form “fingerprints”**
**181****Ta(********’ n) ****180****Ta **
**138****Ba(********e ****,e****- ****) ****138****La**
**20****Ne(********’ n) ****19****Ne       ****19****F**
**12****C(********’ p)****11****B , ****12****C(********’ pn)****10****B**

## Conclusion:Neutrinos are important

**For Super Novae explosion mechanism**
**SN dynamics**
**Nucleosynthesis of heavy elements.**

**To understand those we need to know:**
**Neutrino oscillations parameters.**
** ****Neutrino interactions in the range of SN energies**
**The last one is important contribution to the nuclear theory **

## SN neutrino energies

**SN neutrino energies**

**In this region of energy only three nucleus has been measured:**
**d(40%), C(10%), and Fe(50%), and only carbon – published.**

**Core collapse of ~25 solar mass star**

## The Spallation Neutron SourceORNL

**The Spallation Neutron Source****ORNL**

**1.3 GeV proton accelerator**

**Accumulator ring**

**2 MW Mercury target**

## SNS parameters

**SNS parameters**

**Primary proton beam energy - 1.3 GeV**
**Intensity - 9.6 ******** 10****15**** protons/sec**
**Pulse duration - 380ns(FWHM)**
**Repetition rate - 60Hz**
**Total power - 2 MW**
**Liquid Mercury target**
**Number of neutrino produced ~ 3********10****22****/year**

**This is a neutrino factory already under construction !!!**

## Present status

**First beam - 2006, full power - 2008**

## Neutrino Production at SNS

**Neutrino Production at SNS**

**Hg**

******+**

******-**

**99.6%**

******+**

********

********

******e**

********

******-**

- e+

- e-

**94%**

**0.13**

**0.09**

********

**p**

## Actual spectra of neutrinos from SNS

**Energy****	****             ****	****	****Time**

**Actual spectra of neutrinos from SNS**

**Short pulses with the energy similar to SN neutrino spectra**

## SNS is a Unique Neutrino Source

**It will be  the most intense, pulsed, low energy neutrino source in the world!**
**The pulsed source drastically reduces backgrounds from cosmic rays. Reduction is equivalent to 1 km of rock overburden.**
**Beam time structure allows separation of *******************from ************** ******and *********e***** ***
**Spectra of *************,***** ******************and ********e***** *****are well known**
******e**** is highly suppressed**

**SNS is a Unique Neutrino Source**

## Reaction Cross section for these energy is small !!!

******e****e****-**** ******** ********e****e****-**
**********e****-**** ******** ************e****-****	**
******e****12****C ******** ****12****Ngs e****-**
******e****12****C ******** ********e ****12****C*******
**********12****C ******** ************12****C*******
******e****p ******** ne****+**
******e****56****Fe ******** ****56****Co e****-****	**

**0.297********10****-43**** cm****2**
**0.050********10****-43**** cm****2**
**0.92********10****-41**** cm****2**
**0.45********10****-41**** cm****2**
**0.27********10****-41**** cm****2**
**7.2********10****-41**** cm****2**
**~2.5********10****-40**** cm****2**

**However SNS will deliver ~ 3 10****22**** neutrinos per year**
**At such flux**
** ****Carbon at 20 meters yields ~ 1⁄4  interaction per kilogram per year**

## Location of detectors at SNS

- Neutrino emission from the target is isotropic

- Extra advantage for small detector – less background from cosmic rays.
- Not exceedingly close to the target, as some shielding is required to reduce flux of energetic neutrons from spallation target.

** ****Closer => Smaller and Cheaper**

## SNS Target Building

**SNS Target Building**

**Property of BES branch of DOE**
**Neutron beams and users have high priority**

- Our advantage: we do not need beam line !
- We do not want beam line !
- We need a spot on the floor not far away from the target

**Notes:**
00-93

## What do we plan?

**We propose to built protected enclosure**
**At 20 meters from the SNS**
**Bunker with active veto large enough to have two 10-20 t detectors.**
**4.5 ******** 4.5 ******** 6.5 meter outside**
**2.5 ******** 2.5 ******** 5.5 meters inside**
**Two detectors placed one on the top of other**

**First one** **Homogeneous**  “Simple”, light collection technique.
- Liquid, transparent targets
**Second Segmented****:**  More challenging, modular structure with replaceable targets. Detector should have enough mass to provide ~ 1k events per year. Plan is to run one new target every year. First target will be Iron.

## Concept of homogenous detector

- 2d, 12C, 16O, 127I

**Hermetic vessel with good PMT coverage**

**Concept of homogenous detector**

- 300, 8” PMTs
- 40% of photocathode coverage
- ~ 15 t fiducial mass

**3 m**

## Concept of segmented detector

**targets**
- 51V, 27Al, 9Be, 11B, 52Cr,
- 56Fe, 59Co, 209Bi, 181Ta

****

**Active detector – gas tubes**
**Energy measurement - by range**

**Concept of segmented detector**

**e**

**Expected resolution for tubes 10mm and 0.5 mm at 30 MeV is ~ 25%**
**Detector size for 20 t fiducial mass is – 3.0 ******** 2.3 ******** 2.3**
**Expected event rate (for iron target)~16/day:**
**Good separation from neutrons**

## Background estimations

**SNS neutrons.**
**Extra shielding and absorbers will eliminate low energy neutrons**
**Time cut will remove high energy neutrons**
**Cosmic Ray Background:**
**SNS duty factor  is 4********10****-4**
**Active hermetic veto will cut another 99%**
**1 meter of steel overburden will kill hadronic component**
**Our estimations shows that expected number of untagged neutrons events in the detector is - 5 /day. **
**This is already below expected neutrino event rates**
**Extra factor is expected from PID in detectors****.**

## (SNS)2  Schedule

**Detector R&D and design-2003-2006**
**(applying for ORNL LDRD money right now)**
**Detector Construction begins- FY 2006**
**Shielding Enclosure Erection- 2007**
**Detectors Installation Completed- January 2008**
**Detectors Commissioning- Summer 2008**.

**(SNS)****2****  Schedule**

## Conclusion

**Conclusion**

-  We have a unique opportunity to established  program for neutrino- nucleus cross section at very lower energy
-  This will be modest by $, long range program
-  This program will influence Cosmology, Nuclear Astrophysics, and Nuclear theory
-  This program should be done !!!
-  Ideas and collaborators are welcome