# Presentation: 091394

## BETA-BEAMS USING THE TEVATRON

- Andreas Jansson
- Fermilab

- NB. Most of this talk comes from the
- CERN beta beam working group and its web site:
- http://cern.ch/beta-beam
- (especially M. Benedikts NuFact04 talk)

- Proton driver workshop

## Outline

**Intro to beta-beams and the CERN/EU study**
**The baseline scenario, ion choice, main parameters**
**Ion production and acceleration**
**Decay ring design issues**
**Higher gamma beta-beams**
**Physics case**
**Beta beams at Fermilab using the Tevatron?**
**1TeV decay ring on the Fermilab site.**
**Conclusions**

- Proton driver workshop

## Introduction to 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)**
**The baseline scenario**
**Avoid anything that requires a “technology jump” which would cost time and money (and be risky)**
**Make use of a maximum of the existing infrastructure**

*slide from M. Benedikt*

- Proton driver workshop

## Beta-beam baseline design

**Neutrino Source **
**Decay Ring**

**Ion production **ISOL target &   Ion source

**Proton Driver **SPL

**Decay ring**
- B = 1500 Tm B = 5 T          C = 7000 m     Lss = 2500 m
- 6He:    = 150 18Ne:   = 60

**SPS**

**Acceleration to medium energy ** RCS

**PS**

**Acceleration to final energy**
- PS & SPS

**Experiment**

**Ion acceleration **Linac

**Beam preparation **ECR pulsed

**Ion production**

**Acceleration**

**Neutrino source**

*slide from M. Benedikt*

- Proton driver workshop

## Main parameters (1)

**Ion choice****	**
**Possibility to produce reasonable amounts of ions**
**Noble gases preferred - simple diffusion out of target, gas phase at room temperature**
**Not too short half-life to get reasonable intensities**
**Not too long half-life as otherwise no decay at high energy**
**Avoid potentially dangerous and long-lived decay products**
**Best compromise**
**6****Helium****2+**** to produce antineutrinos:**
**18****Neon****10+ ****to produce neutrinos:**

*slide from M. Benedikt*

- Proton driver workshop

## Main parameters (2)

**Target values in the decay ring****	**

**18****Neon****10+ ****(single target)**
**Intensity (av.):    4.5x10****12**** ions **
**Energy:****	****           55 GeV/u**
**Rel. gamma:         60****	**
**Rigidity:****	****           335 Tm **

**6****Helium****2+**
**Intensity (av.):    1.0x10****14**** ions **
**Energy:****	****           139 GeV/u**
**Rel. gamma:        150****	**
**Rigidity:****	****          1500 Tm **

**The neutrino beam at the experiment has the “time stamp”      of the circulating beam in the decay ring.**
**The beam has to be concentrated in as few and as short bunches as possible to maximize the peak number of ions/nanosecond (background suppression). **
**Aim for a duty factor of 10****-4**** -> this is a major design challenge!**

*slide from M. Benedikt*

- Proton driver workshop

## Ion production - ISOL method

**Isotope Separation OnLine method.**
**Few GeV proton beam onto fixed target.****	**

- 18Ne directly
- 6He via spallation n

*slide from M. Benedikt*

- Proton driver workshop

## 6He production from 9Be(n,)

**Converter technology preferred to direct irradiation (heat transfer and efficient cooling allows higher power compared to insulating BeO).**
**6****He production rate is ~2x10****13**** ions/s (dc) for ~200 kW on target.**

- Converter technology: (*J. Nolen, NPA 701 (2002) 312c*)

*slide from M. Benedikt*

- Proton driver workshop

## 18Ne production

**Spallation of close-by target nuclides:****18****Ne from MgO:**
**24****Mg****12**** (p, p****3**** n****4****) ****18****Ne****10**
**Direct target: no converter technology can be used, the beam hits directly the oxide target.**
**Production rate for ****18****Ne is ~ 1x10****12**** ions/s                       (200 kW dc proton beam at a few GeV beam energy).**
**19****Ne can be produced with one order of magnitude higher intensity but the half life is 17 seconds!**

*slide from M. Benedikt*

- Proton driver workshop

## From dc ions to very short bunches

*slide from M. Benedikt*

- Proton driver workshop

## Decay ring design aspects

**The ions have to be concentrated in very few very short bunches.**
**Suppression of atmospheric background via time structure.**
**There is an absolute need for stacking in the decay ring.**
**Not enough flux from source and injection chain.**
**Life time is an order of magnitude larger than injector cycling (120 s as compared to 8 s SPS cycling).**
**We need to stack at least over 10 to 15 injector cycles.**
**Cooling is not an option for the stacking process:**
**Electron cooling is excluded because of the high electron beam energy and in any case far too long cooling times.**
**Stochastic cooling is excluded by the high bunch intensities.**
**Stacking without cooling creates “conflicts” with Liouville.**

*slide from M. Benedikt*

- Proton driver workshop

## Full scale simulation for SPS

*slide from M. Benedikt*

- Proton driver workshop

## Test experiment in CERN PS

- Merging of circulating bunch with empty phase space.
- Longitudinal emittances are conserved
- Negligible blow-up

*slide from M. Benedikt*

- Proton driver workshop

## Decay ring arc lattice design

**FODO structure**
**Central cells detuned for injection**
**Arc length ~984m**
**Bending 3.9 T, ~480 m l****eff**
**5 quadrupole families**

- A. Chance, CEA-Saclay (F)

*slide from M. Benedikt*

- Proton driver workshop

## Radiation protection - decay losses

**Losses during acceleration **
**Full FLUKA simulations in progress for all stages (M. Magistris and M. Silari, *****Parameters of radiological interest for a beta-beam decay ring*****, TIS-2003-017-RP-TN)**
**Preliminary results:**
**Manageable in low energy part**
**PS heavily activated (1s flat bottom)**
**Collimation? New machine?**
**SPS ok.**
**Decay ring losses: **
**Tritium and Sodium production in rock well below national limits**
**Reasonable requirements for tunnel wall thickness to enable decommissioning of the tunnel and fixation of Tritium and Sodium**

**FLUKA simulated losses in surrounding rock (no public health implications)**

*slide from M. Benedikt*

- Proton driver workshop

## Future R&D

**Future beta-beam R&D together with EURISOL project**
**Design Study in the 6th Framework Programme of the EU**
**The EURISOL Project**
**Design of an ISOL type (nuclear physics) facility **
**Performance three orders of magnitude above existing facilities**
**A first feasibility / conceptual design study was done within FP5**
**Strong synergies with the beta-beam especially low energy part:**
**Ion production (proton driver, high power targets)**
**Beam preparation (cleaning, ionization, bunching)**
**First stage acceleration (post accelerator ~100 MeV/u)**
**Radiation protection and safety issues**

*slide from M. Benedikt*

- Proton driver workshop

## Physics Reach

- Physics reach of SPS-> Frejus beta-beam similar to super-beam.
- May reduce systematics by combining the two
- Energy resolution in detector washed out by Fermi motion due to low energy.
- Go to higher energies.

- Proton driver workshop

## 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) ***

- Proton driver workshop

## Higher energy beta-beams (2)

- “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?

- Proton driver workshop

## Radioactive beams in the Tevatron?

- Generic and fundamental questions will be addressed by the CERN/EU study
- Fermilab specific questions:
- How much radioactive beam can the Tevatron accelerate without quenching due to decay losses?
- (N. Mokhov, answer expected early 2005)
- Is it feasible to build a 1TeV (proton equivalent) decay ring with reasonable efficiency at the Fermilab site?
- ...

- Proton driver workshop

## 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 other machines smaller.

| 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+

- Proton driver workshop

## 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**

- Proton driver workshop

## 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!**

- Proton driver workshop

## 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).

- Proton driver workshop

## Ion intensities

- The comparative study assumed same number of decays/year for all three scenarios.
- Same production rate, but equilibrium stack will be correspondingly more intense, as particles live longer at higher gamma.
- Only 1⁄4 of decays in the right direction
- Need to reduce bending radius, or increase the ion production rate by x2 to compensate.
- May be issue with space charge
- Higher gamma option may not need as short and few bunches.

- Proton driver workshop

## Conclusions

**If the physics case for Tevatron-energy beta beams is confirmed by more detailed studies, it may be an interesting future option for Fermilab.**
**1TeV decay ring of ~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.**
**A proton driver would be part of the scenario, albeit with a relatively modest power (~0.5 MW).**

*slide from M. Benedikt*

- Proton driver workshop