# Presentation: 091392

## BETA-BEAMS IN THE TEVATRON?

- Andreas Jansson
- Fermilab

- APD meeting

## Beta-beams

**Beta-beam proposal by Piero Zucchelli:**
***A novel concept for a neutrino factory: the beta-beam*****,        Phys. Let. B, 532 (2002) 166-172.**
**AIM: production of pure beams of electron neutrinos (or antineutrinos) from the beta decay of radioactive ions, circulating in a high energy decay ring (********~100)**
**Best ion candidates**
**6****Helium****2+**** to produce antineutrinos:**
**18****Neon****10+ ****to produce neutrinos:**
**Physics case relies on timing for background suppression (few short bunches in decay ring).**

- APD meeting

## CERN/EURISOL Study

- Aiming for an annual* rate of 2.9 1018 anti-neutrinos (6He) and 1.1 1018 neutrinos (18Ne) at =100.
- Current status:
- Claim to have feasible concept for 6He, but no intensity margin yet.
- Difficulty to achieve 18Ne goal (factor 20 below), mainly due to limited production rate, but also space charge limitations.

- http://cern.ch/beta-beam

***1 year = 1e7 seconds**

- APD meeting

## Higher energy beta-beams

**‘****Original’ energy scale was set by SPS. **
**Potential of higher energies studied by Burguet-Castell *****et al***
***Neutrino oscillation physics with a higher gamma beta-beam*****, Nucl.Phys.B695:217-240,2004.**
**Three scenarios studied:**
*********(He)=60, ************(Ne)=100, L=130km (CERN/SPS-Frejus)***
*********(He)=350, ************(Ne)=580, L=732km (FNAL/Tev-Soudan)***
*********(He)=1500, ************(Ne)=2500, L=3000km (CERN/LHC-Canary Islands) ***

- APD meeting

## Higher energy beta-beams II

- “Our results show that the intermediate  option is spectacularly better than the low  option previously considered, both in terms of the reach in CP violation as in the possibility to measure the neutrino mass hierarchy”**	****	****	****	****Nucl.Phys.B695:217-240,2004**
- Is it possible in practice?

- APD meeting

## Radioactive beams in the Tevatron?

- Generic and fundamental questions are addressed by the CERN/EURISOL study
- Fermilab specific questions:
- Is it feasible to build a 1TeV (proton equivalent) decay ring with reasonable efficiency at the Fermilab site?
- What neutrino flux is needed at Tevatron energies for a good physics case?
- How much radioactive beam can the Tevatron accelerate without quenching due to decay losses?

- APD meeting

## Site constraints

**“****Stretched Tevatron“ aimed **
**at Soudan**
**B******** = 3335 Tm**
**R = **_**1000 m**_** (75% 4.4T dipoles)**
**L****SS****= ~3500**
**Total circumference:**
**   ****approximately 2 x Tevatron**
**320m elevation @ 58 mrad **
**26% of decays in SS**

- APD meeting

## Geology constraints

- Glacial till

- Silurian group (dolomite)

- Maquoketa group (shale)

- Galena/Platteville group
- (dolomite)

- Ancel group (sandstone)

- NB. Vertical scale enhanced x10

-      For a shallow angle (Soudan),
-    a non-planar machine utilizes
-  available depth better, due to
- the large bending radius.

*7% **→** 26% for Tevatron radius*

**Only ~200m of “good rock” available!**

- APD meeting

## Optics

- Toy optics design
- Matching doublet
- Dispersion free vertical bends
- Horizontal dispersion suppressor
- Tevatron B-fields and gradients
- Efficiency 25% -> 21%, may be increased with higher B-field (shorter arcs).

- APD meeting

## What flux is needed?

- Working number ~1e18 neutrinos/year, with a duty factor of 1e-3.
- TH friends are looking to refine numbers
- Is it possible with Tevatron?
- 1e11 neutrinos/second, or 5e12 per Tevatron ramp (assuming 50s cycle time)
- Only ~25% of decays in right direction, hence ~2e13 needed per ramp.

- APD meeting

## Decay losses during acceleration 

- Back-of-the-envelope estimate of decay losses in the acceleration chain seem manageable.
- About ~1 1013 ions of either type per cycle should yield an average loss power of about 1 W/m.
- Loss power in the other machines smaller.
- NEED REALISTIC SIMULATION!!!

| Machine | Ramp time | Gamma | Est. Loss |
| --- | --- | --- | --- |
| Booster | 0.03 s | 3.3 / 5.4  | 2 % / 1 % |
| Main Injector | 0.7 s | 64 / 89  | 2 % / 1 % |
| Tevatron | 17 s | 349 / 581 | 10 % / 3 % |

-  values are for 6He2+ / 18Ne10+

- APD meeting

## Conclusions

**If the physics case for Tevatron-energy beta beams is confirmed by more detailed studies, it could be an interesting future option for Fermilab.**
**1TeV decay ring with ~21% efficiency fits on site (efficiency may be improved with higher field magnets).**
**Many more questions need to be addressed regarding the feasibility of the scheme, and the possibility of using existing Fermi machines.**
**Next step is realistic simulation of decay losses**

- APD meeting

## Space charge

- To get 1e11 decays/s, 3.5e13 6He at γ=350, and 1.2e14 18Ne at γ=500.
- Few short bunches (duty factor 1e-3) required, hence high density. Also high charge state.
- Taking the emittance to be 100π, space charge tune shift is 0.01 for 6He, and 0.7 for 18Ne. The latter is clearly a problem.

- APD meeting