1. The beta-beam
Mats Lindroos
CERN
GSI, 17 January 2005
Mats Lindroos

2. Evolution of the beta-beam Conclusions
Outline
Beta-beam
EURISOL DS beta-beam: ion choice, main parameters
Ion production
Asymmetric bunch merging for stacking in the decay ring
Decay ring optics design & injection
Evolution of the beta-beam
Conclusions
GSI, 17 January 2005
Mats Lindroos

3. Exists in at least three flavors (e, m, t)
Neutrinos
A mass less particle predicted by Pauli to explain the shape of the beta spectrum
Exists in at least three flavors (e, m, t)
Could have a small mass which could significantly contribute to the mass of the universe
The mass could be made up of a combination of mass states
If so, the neutrino could “oscillate” between different flavors as it travel along in space
GSI, 17 January 2005
Mats Lindroos

4. Neutrino oscillations CKM in quark sector -> MNS in neutrino sector
Three neutrino mass states (1,2,3) and three neutrino flavors (e,m,t)
OR?
Dm223= eV2
Dm212= eV2 n1 n2 n3
q23 (atmospheric) = 450 , q12 (solar) = 300 , q13 (Chooz) < 130
Unknown or poorly known
even after approved program:
13 , phase  , sign of Dm13 2
GSI, 17 January 2005
Mats Lindroos
A. Blondel

5. 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)
AIM: production of a pure beam of electron neutrinos (or antineutrinos) through the beta decay of radioactive ions circulating in a high-energy (~100) storage ring.
First study in 2002
Make maximum use of the existing infrastructure.
boost n
6He
Beta-beam
GSI, 17 January 2005
Mats Lindroos

6. Factors influencing ion choice
Main parameters
Factors influencing ion choice
Need to produce reasonable amounts of ions.
Noble gases preferred - simple diffusion out of target, gaseous 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
Helium-6 to produce antineutrinos:
Neon-18 to produce neutrinos:
GSI, 17 January 2005
Mats Lindroos

7. The first study “Beta-beam” was aiming for:
Annual rate
The first study “Beta-beam” was aiming for:
A beta-beam facility that will run for a “normalized” year of 107 seconds
An annual rate of anti-neutrinos (6He) and neutrinos (18Ne) at g=100
with an Ion production in the target to the ECR source:
6He= atoms per second
18Ne= atoms per second
The often quoted beta-beam facility flux for ten years running is:
Anti-neutrinos: decays along one straight section
Neutrinos: decays along one straight section
GSI, 17 January 2005
Mats Lindroos

8. Post system Gas catcher Driver-beam
In-flight and ISOL
“ISOL: Such an instrument is essentially a target, ion source and an electromagnetic mass analyzer coupled in series. The apparatus is aid to be on-line when the material analyzed is directly the target of a nuclear bombardment, where reaction products of interest formed during the irradiation are slowed down and stopped in the system.
H. Ravn and B.Allardyce, 1989, Treatise on heavy ion science
In-Flight:
ISOL:
Post
system
Gas catcher
Driver-beam
Thin target
Thick hot ISOL target
GSI, 17 January 2005
Mats Lindroos

9. 6He production from 9Be(n,a)
Converter technology: (J. Nolen, NPA 701 (2002) 312c)
Converter technology preferred to direct irradiation (heat transfer and efficient cooling allows higher power compared to insulating BeO).
6He production rate is ~2x1013 ions/s (dc) for ~200 kW on target.
GSI, 17 January 2005
Mats Lindroos

10. Producing 18Ne and 6He at 100 MeV
Work within EURISOL task 2 to investigate production rate with “medical cyclotron”
Louvain-La-Neuve, M. Loislet
GSI, 17 January 2005
Mats Lindroos

11. From dc to very short bunches…
…or how to make meatballs out of wurst!
Radioactive ions are usually produced as a “dc” beam but synchrotrons can only accelerate bunched beams.
For high energies, linacs are long and expensive, synchrotrons are cheaper and more efficient.
GSI, 17 January 2005
Mats Lindroos

12. 60 GHz « ECR Duoplasmatron » for gaseous RIB
2.0 – 3.0 T pulsed coils
or SC coils
Very high density
magnetized plasma
ne ~ 1014 cm-3
Small plasma
chamber F ~ 20 mm / L ~ 5 cm
Target
Arbitrary distance
if gas
Rapid pulsed valve ?
1-3 mm
100 KV
extraction
UHF window
or « glass » chamber (?)
20 – 100 µs
20 – 200 mA
1012 per bunch
with high efficiency
60-90 GHz / KW
10 –200 µs /  = 6-3 mm
optical axial coupling
optical radial (or axial) coupling
(if gas only)
P.Sortais et al.
GSI, 17 January 2005
Mats Lindroos

13. From dc to very short bunches
2 ms t B PS
SPS
20 bunches
PS: 1 s flat bottom with 20 injections. Acceleration in ~1 s to ~86.7 Tm..
Target: dc production during 1 s.
60 GHz ECR: accumulation for 1/20 s ejection of fully stripped ~50 ms pulse.
20 batches during 1 s.
RCS: further bunching to ~100 ns Acceleration to ~ 8 Tm.
16 repetitions during 1 s.
SPS: injection of 20 bunches from PS. Acceleration to decay ring energy and ejection.
7 s
Post accelerator linac: acceleration to ~100 MeV/u repetitions during 1 s.
GSI, 17 January 2005
Mats Lindroos

14. What is important for the decay ring?
The atmospheric neutrino background is large at 500 MeV, the detector can only be open for a short moment every second
The decay products move with the ion bunch which results in a bunched neutrino beam
Low duty cycle – short and few bunches in decay ring
Accumulation to make use of as many decaying ions as possible from each acceleration cycle
Ions move almost at the speed of light
Only “open” when neutrinos arrive
GSI, 17 January 2005
Mats Lindroos

15. Decay ring design aspects
The ions have to be concentrated in a few very short bunches
Suppression of atmospheric background via time structure.
There is an essential need for stacking in the decay ring
Not enough flux from source and injector chain.
Lifetime is an order of magnitude larger than injector cycling (120 s compared with 8 s SPS cycle).
Need to stack for at least 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, the cooling time is far too long.
Stochastic cooling is excluded by the high bunch intensities.
Stacking without cooling “conflicts” with Liouville
GSI, 17 January 2005
Mats Lindroos

16. Asymmetric bunch pair merging
Moves a fresh dense bunch into the core of the much larger stack and pushes less dense phase space areas to larger amplitudes until these are cut by the momentum collimation system.
Central density is increased with minimal emittance dilution.
Requirements:
Dual harmonic rf system. The decay ring will be equipped with 40 and 80 MHz systems (to give required bunch length of ~10 ns for physics).
Incoming bunch needs to be positioned in adjacent rf “bucket” to the stack (i.e., ~10 ns separation!).
GSI, 17 January 2005
Mats Lindroos

17. Simulation (in the SPS)
GSI, 17 January 2005
Mats Lindroos

18. Test experiment in CERN PS
Ingredients
h=8 and h=16 systems of PS.
Phase and voltage variations.
time
energy
S. Hancock, M. Benedikt and J-L.Vallet, A proof of principle of asymmetric bunch pair merging, AB-Note MD
GSI, 17 January 2005
Mats Lindroos

19. Ring optics Beam envelopes Arc optics
In the straight sections, we use FODO cells. The apertures are ±2 cm in the both plans
The arc is a 2 insertion composed of regular cells and an insertion for the injection.
There are 489 m of 6 T bends with a 5 cm half-aperture.
At the injection point, dispersion is as high as possible (8.25 m) while the horizontal beta function is as low as possible (21.2 m).
The injection septum is 18 m long with a 1 T field.
Arc optics
A. Chancé, J. Payet

20. Injection Horizontal envelopes at injection
Injection is located in a dispersive area
The stored beam is pushed near the septum blade with 4 “kickers”. At each injection, a part of the beam is lost in the septum
Fresh beam is injected off momentum on its chromatic orbit. “Kickers” are switched off before injected beam comes back
During the first turn, the injected beam stays on its chromatic orbit and passes near the septum blade
Injection energy depends on the distance between the deviated stored beam and the fresh beam axis
envelopes (cm)
Injected beam
Septum blade
Injected beam
after one turn
Deviated beam
s (m)
Optical functions in the injection section
A. Chancé, J. Payet

21. The EURISOL beta-beam facility!
GSI, 17 January 2005
Mats Lindroos

22. (September 2005)
GSI, 17 January 2005
Mats Lindroos

23. GSI, 17 January 2005
Mats Lindroos

24. Subtasks within beta-beam task
Beta-beam R&D
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 low-energy part of the beta-beam:
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.
Subtasks within beta-beam task
ST 1: Design of the low-energy ring(s).
ST 2: Ion acceleration in PS/SPS and required upgrades of the existing machines including new designs to eventually replace PS/SPS.
ST 3: Design of the high-energy decay ring.
Around 38 (13 from EU) man-years for beta-beam R&D over next 4 years (only within beta-beam task, not including linked tasks).
GSI, 17 January 2005
Mats Lindroos

25. Design study objectives
Establish the limits of the first study based on existing CERN accelerators (PS and SPS)
Freeze target values for annual rate at the EURISOL beta-beam facility
Close cooperation with neutrino physics community
Freeze a baseline for the EURISOL beta-beam facility
Produce a Conceptual Design Report (CDR) for the EURISOL beta-beam facility
Produce a first cost estimate for the facility
GSI, 17 January 2005
Mats Lindroos

26. Challenges for the study
Production
Charge state distribution after ECR source
The self-imposed requirement to re-use a maximum of existing infrastructure
Cycling time, aperture limitations etc.
The small duty factor
The activation from decay losses
The high intensity ion bunches in the accelerator chain and decay ring
GSI, 17 January 2005
Mats Lindroos

27. Workshop at LLN for production, ionization and bunching this spring
Major challenge for 18Ne
Workshop at LLN for production, ionization and bunching this spring
New production method proposed by C. Rubbia!
GSI, 17 January 2005
Mats Lindroos

28. Charge state distribution!
GSI, 17 January 2005
Mats Lindroos

29. Losses during acceleration
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 RP-TN).
Preliminary results:
Manageable in low-energy part.
PS heavily activated (1 s flat bottom).
Collimation? New machine?
SPS ok.
Decay ring losses:
Tritium and sodium production in rock is well below national limits.
Reasonable requirements for tunnel wall thickness to enable decommissioning of the tunnel and fixation of tritium and sodium.
Heat load should be ok for superconductor.
FLUKA simulated losses in surrounding rock (no public health implications)
GSI, 17 January 2005
Mats Lindroos

30. Decay products extraction
Fluorine extraction
Two free straight sections after the first arc dipole enable the extraction of decay products coming from long straight sections.
The decay product envelopes are plotted for disintegrations at the begin, the middle and the end of the straight section.
Fluorine extraction needs an additional septum.
The permanent septum for Fluorine extraction is 22.5 m long and its field is 0.6 T.
Lithium extraction can be made without a septum.
Lithium extraction
A. Chancé, J. Payet

31. Decay products deposit in the arc
Deviation of one decay product by one bend as a function of its length
The dispersion after a L long bend with a radius equal to ρ is :
By this way, we can evaluate the maximum length of a bend before the decay products are lost there.
If we choose a 5 cm half aperture, half of the beam is lost for a 7 m long bend. With a 5 m long bend, there is very low deposits in the magnetic elements.
Lithium deposit (W/m)
Only the Lithium deposit is problematic because the Neon intensity is far below the Helium one.
A. Chancé, J. Payet

32. Duty factor
A small duty factor does not only require short bunches in the decay ring but also in the accelerator chain
Space charge limitations
GSI, 17 January 2005
Mats Lindroos

33. Space charge tune shift
Using existing PS and SPS, version 2 Space charge limitations at the “right flux”
Transverse emittance normalized to PS acceptance at injection for an annual rate of 1018 (anti-) neutrinos
Space charge tune shift
Note that for LHC the corresponding values are and -0.34
GSI, 17 January 2005
Mats Lindroos

34. A tool to identify the right parameters for a design study
“Trend curves”
A tool to identify the right parameters for a design study
Does not in themselves guarantee that a solution can be found!
Requires a tool to express the annual rate as a function of all relevant machine parameters
psacceleration := (ClearAll[n];
psTpern[t_] := psinjTpern +
(spsinjTpern - psinjTpern) t/psaccelerationtime;
gamma[t_] := 1 + psTpern[t] / Epern;
decayrate[t_] := Log[2] n[t] / (gamma[t] thalf);
eqns = {D[n[t], t] == -decayrate[t], n[0]==nout3};
n[t_] = n[t] /. DSolve[eqns, n[t], t] //First;
nout4 = n[psaccelerationtime] )
GSI, 17 January 2005
Mats Lindroos

35. Gamma and duty cycle
GSI, 17 January 2005
Mats Lindroos

36. The slow cycling time. What can we do?
Ramp time PS
Reset time SPS
Ramp time SPS
Decay ring
SPS PS
Production
Wasted time? 8
Time (s)
GSI, 17 January 2005
Mats Lindroos

37. T1/2=1.67 s T1/2=17 s T1/2=0.67 s Accumulation at 400 MeV/u
GSI, 17 January 2005
Mats Lindroos

38. Multiturn injection with electron cooling
Stacking
Multiturn injection with electron cooling
GSI, 17 January 2005
Mats Lindroos

39. Accumulation of 19Ne
The annual neutrino rate as a function of the accumulation time in the EC-RCS and stacked in PS at 10 Hz injection.
The annual rate depends on the combined effects of the whole accelerator chain.
GSI, 17 January 2005
Mats Lindroos

40. Accumulation of 19Ne
The annual neutrino rate as a function of the number of ECR bunches accumulated in the EC-RCS and stacked in SPS
GSI, 17 January 2005
Mats Lindroos

41. Flux as a function of gamma
Where are we now, 6He ?
Flux as a function of gamma
Flux as a function of accumulation time in PS
Flux as a function of duty cycle
GSI, 17 January 2005
Mats Lindroos

42. Flux as a function of gamma
Where are we now, 18Ne ?
Flux as a function of gamma
Flux as a function of accumulation time in PS
N.B. 3 charge states through the linac!
Flux as a function of duty cycle
GSI, 17 January 2005
Mats Lindroos

43. Beyond the EURISOL beta-beam facility
Energy, intensity, physics reach, detection method, experiment…
GSI, 17 January 2005
Mats Lindroos

44. EC: A monochromatic neutrino beam
GSI, 17 January 2005
Mats Lindroos

45. Beyond EURISOL DS: Who will do the design? Is 150Dy the best isotope?
Partly stripped ions: The loss due to stripping smaller than 5% per minute in the decay ring
Possible to produce Dy atoms/second (1+) with 50 microAmps proton beam with existing technology (TRIUMF)
An annual rate of 1018 decays along one straight section seems as a realistic target value for a design study
Beyond EURISOL DS: Who will do the design?
Is 150Dy the best isotope?
GSI, 17 January 2005
Mats Lindroos

46. Long half life – high intensities
At a rate of 1018 neutrinos using the EURISOL beta-beam facility:
GSI, 17 January 2005
Mats Lindroos

47. Gamma and decay-ring size, 6He
Rigidity
[Tm]
Ring length
T=5 T
f=0.36
Dipole Field
rho=300 m
Length=6885m
100
938
4916
3.1
150
1404
6421
4.7
200
1867
7917
6.2
350
3277
12474
10.9
500
4678
17000
15.6
New SPS
Civil engineering
Magnet R&D
GSI, 17 January 2005
Mats Lindroos

48. Gamma and annual rate, 6He
Nominal duty cycle (saturates at 4 x)
We must increase production!
GSI, 17 January 2005
Mats Lindroos

49. n n The proposal Physics potential ne Beta-beam
Low energy beta-beam
The proposal
To exploit the beta-beam concept to produce intense and pure low-energy neutrino beams (C. Volpe, hep-ph/ , To appear in Journ. Phys. G. 30(2004)L1)
Physics potential
Neutrino-nucleus interaction studies for particle, nuclear physics, astrophysics (nucleosynthesis)
Neutrino properties, like n magnetic moment
boost n
6He
Beta-beam N
6He
6Li+e+ne Qb=4. MeV ne e n
GSI, 17 January 2005
Mats Lindroos

50. Time scale? Physics? Which option? What to conclude?
GSI, 17 January 2005
Mats Lindroos

51. In 2008 we should know
The EURISOL design study will with the very limited resources available give us:
A feasibility study of the CERN-Frejus baseline
A first idea of the total cost
An idea of how we can go beyond the baseline
Resources and time required for R&D
Focus of the R&D effort
Production, Magnets etc.
GSI, 17 January 2005
Mats Lindroos

52. Is there a feasible detector design?
We need to know for 2008
Is there a feasible detector design?
Site of the detector and cost
Is there a physics case for the beta-beam
The CERN Frejus baseline?
Other options?
For other options
What gamma, duty-factor and intensity do you require
Carlo Rubbia beta-beam
When will we know if there is a physics case?
Theta_13
GSI, 17 January 2005
Mats Lindroos

53. Theta13
GSI, 17 January 2005
Mats Lindroos

54. Present physics reach
GSI, 17 January 2005
Mats Lindroos

55. The EURISOL beta-beam facility is our “study 1”
Conclusions
The EURISOL beta-beam facility is our “study 1”
The beta-beam concept is extremly rich
Low energy beta-beams
Monochromatic beta-beams
High gamma beta-beams
Carlo Rubbia beta-beam
Do you have an idea!
Welcome to the world of beta-beams!
GSI, 17 January 2005
Mats Lindroos