Neutrino Factory Decay Rings Studies in the framework of IDS-NF - - PowerPoint PPT Presentation

Neutrino Factory Decay Rings

Studies in the framework of IDS-NF

David Kelliher*, Jaroslaw Pasternak^ (presenter) *RAL/ASTeC/STFC ^Imperial College London/STFC 20/6/13, MAP meeting, Fermilab

Our collaboration working on the Decay Ring within the IDS-NF

Introduction – Decay Ring

Design Aims Reasonable neutrino production efficiency (η) Low beam divergence in production straight (<0.1/γ) Maintain bunch separation (100 ns) Allow realistic injection scheme

• 25 GeV design

Optics of 10 GeV Ring

10 GeV decay ring design (No insertion)

0.0 1. 2. 3. 4. 5. 6. 7. 8.

s (m) Decay Ring MAD-X 5.00.00 06/04/13 12.58.36

2.0 3.1 4.2 5.3 6.4 7.5 8.6 9.7 10.8 11.9 13.0

b

x (m), b y (m)

0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4

D

x (m)

b x b y Dx

Arc

Length Field/Gradien t Drift 0.3 m

• Dipole

2.35 m 1.46 T Quad F&D 0.8 m +/-14.78 T/m Beam envelope in quads 6.0 cm

Ideal bunch crossing points

LLL

• When muon bunches are equally spread around the ring, two must be at arc centres

to ensure equally spaced neutrino bursts.

• Bunches must cross at centre of production straight and ±L/6 away where L is the

ring circumference.

• If η≥2/3, all crossing points will lie in production straight.

Injection timing

• Injection delay L/(6c)
• Kicker rise/fall time is L/(6c) -tbunch
• Simultaneous injection
• Kicker rise/fall time is L/(3c) -tbunch

Inject in between crossing points Inject into crossing points In both cases delay between consecutive pairs of bunches is (n + 1/3)*L

Injection into production straight (1)

• Ensure left-right symmtry for both sign injection – change

lattice from FODO to FDDF.

• Injection section F-S-D-K-D-S-F
• Qx,Qy = 0.094, 0.084

0.0 5. 10. 15. 20. 25. 30. 35. 40.

s (m) Decay Ring MAD-X 5.00.00 02/04/13 17.26.25

50.0 53.5 57.0 60.5 64.0 67.5 71.0 74.5 78.0 81.5 85.0

b

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

D

b x b y Dx

Lengt h (m) Gradient (T/m) Aperture

1.3*√(εβ) (m)

D 2.0

• 0.34

0.207 F 2.0 0.68 0.213 Drift 10.0

Injection into production straight (2)

• Ensure 2cm separation

between injected and circulating beam at septum exit.

• Injected beam excursion

in kicker magnet 9.5 cm, in D magnet 15.2 cm.

0.0 5. 10. 15. 20. 25. 30. 35. 40.

s (m) Decay Ring MAD-X 5.00.00 05/04/13 15.18.45

0.0 0.1 0.2 0.3 0.4 0.5 0.6

x (m)

• 0.8
• 0.7
• 0.6
• 0.5
• 0.4
• 0.3
• 0.2
• 0.1

0.0

D

x (m)

x Dx

Length (m) Field (T) Angle (rad) Kicker 8.8 0.08 0.022 Septum 1.6 3.06 0.147

Kicker design for 25 GeV muon FFAG

Table XXVIII. Parameters of the kicker system Kicker total aperture (h× v) 0.3× 0.3 m Kicker length 4.4 m Rise/ fall time (5-95%) 1.9 µs Kicker max field ≈ 0.1 T Kicker pulse duration at the top 0.3 µs Charging voltage 60 kV Peak current in the magnet 30 kA Kicker inductance 5.1 µH Kicker impedance 1 Ω Peak current at switch 10 kA Repetition rate 50 Hz Number of sub-kickers 4-5 Number of PFNs per micro-pulse per sub-kicker 3 Total number of PFNs 36 (for 4 sub-kickers) Total averaged power per kicker ≈ 1.25 MW Total peak power per kicker ≈ 2.5 MW

= 0 µs = 120 µs = 240 µs Ω Ω

Decay ring injection at the production straight requirements Kicker aperture 0.44 x 0.34 m Rise/fall time 0.8 us Difficult!

Injection into insertion Injecting bunches simultaneously (1)

• Distance of injection point from arc center Δx

should be enough to allow bunch separation at end of production straights.

• Assuming 100ns minimum gap between

signals for 4 mean lifetimes, and phase slip 0.005 then Δx = 83.7m.

• In current design half the arc is 53.1m, so

injection point should be 30.6m further away from end of arc.

Dx = c 2 tb

ini +nth dp

p To +tgap æ è ç ö ø ÷

Δx

ν ν

Injection into insertion Injecting bunches simultaneously (2)

• Distribution of bunch crossing points

is left-right assymetric, in general.

• Means neutrino bursts separated by

two different time intervals which alternate.

• Time separation is still more than the

100 ns required by detectors.

Δx

ν ν

Triplet magnet modules

Empty space

Kickers

Matching to the arc Matching to the straight

Septa

Conceptual layout of the injection insertion

• Arc-type cells are to compact and straight cells has very large beam size and non-ideal

phase advance for injection.

• Insertion based on triplets may provide additional length in the drift and phase advance

can be optimised.

• Two kickers and two septa are needed in a symmetric configuration.

5 10 15 20 s m 0.2 0.4 0.6 0.8 1 1.2 D m

10 20 30 40 50 60 s m 2.5 5 7.5 10 12.5 15 17.5 20 m

Dispersion matching at the end of the arc Adding one more FODO cell and changing the dipole strength (relaxing some values)

Injection insertion matched to the arc Matching to the straight: work in progress...

Optics of the injection straight

Ring with insertion

Circumference 1575.8 Production efficiency 35.56% x 2 Total tune 14.25, 14.88 Phase slip 2.8 x 10-3 Turns per mean lifetime 39.6

• The insertion is located at either end of the upper arc. One insertion is

used for injection, the other is included for left-right symmetry.

• The insertion is made up of four identical FDF Triplet cells with 5.6m

long drift.

Angle (mrad) Length (m) Field (T) τrise/fall μs Septum 67.5 3.0 0.75

• Kicker

8.1 5.4 0.05 1.37

Insertion

Injected beam trajectory

0.0 10.18 20.36 30.54 40.72 50.90

s (m) Decay Ring MAD-X 5.00.00 10/05/13 13.07.03

• 0.10
• 0.05

0.0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

x (m)

x

Injection trajectory of beam centroid. The injected beam is travelling from right to left.

Decay Ring Injection Kickers Towards the realistic kicker parameters

No of kickers 2 No of sub kickers 10 PFNs per kicker sub units 3 No of Pulse Forming Networks 30 Thyratrons 30 Travelling wave system design B field 0.06 T

Kicker aperture 0.18 x 0.18 m Kicker length 5.4 m Rise/Fall (5-95%) 1370 ns Pulse duration at top 0.3 µS

Upper Arc

• Dispersion suppressor at

either end of upper arc to eliminate dispersion before entering insertion. This should be further optimised.

• Optics matching from

insertion to adjacent sections.

• Matching to production

straight contains reverse bend to help collimate stray electrons and muons.

0.0 50. 100. 150. 200. 250. 300.

s (m) Decay Ring MAD-X 5.00.00 08/05/13 16.11.47

0.0 10. 20. 30. 40. 50. 60. 70. 80. 90. 100.

b

x (m), b y (m)

• 0.2

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

D

x (m)

b x b y Dx

Lower Arc

• There is no need for insertions in

lower part of the ring.

• The insertion contributes to the

width of the racetrack since the arcs bend by less than 180

• degrees. The lower arc should be

scaled up to match this extra width.

• In order to use the same magnets

as upper arc, just the drift lengths are scaled up. However, the focusing is adjusted by a small amount to optimise the working point.

0.0 40. 80. 120. 160.

s (m) Decay Ring MAD-X 5.00.00 09/05/13 23.19.48

0.0 9. 18. 27. 36. 45. 54. 63. 72. 81. 90.

b

x (m), b y (m)

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

D

x (m)

b x b y Dx

Conclusions

• Injection into the production straight requires large

aperture kickers with <1μs rise/fall time.

• Instead we consider adding an injection insertion.

This adds to the decay ring circumference but allows a realistic injection scenario.

• Decay ring could be smaller (even by a factor of two),

if single bunch could be used (like for a Muon Collider). Arc magnets could have higher field.