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 25 GeV design 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

10 GeV decay ring design (No insertion) Optics of 10 GeV Ring

Arc Decay Ring MAD-X 5.00.00 06/04/13 12.58.36 13.0 1.4 y (m) x (m) b x b y D x 11.9 D x (m), b 1.3 10.8 b 1.2 9.7 8.6 1.1 Length Field/Gradien 7.5 t 1.0 6.4 Drift 0.3 m - 5.3 0.9 Dipole 2.35 m 1.46 T 4.2 Quad F&D 0.8 m +/-14.78 T/m 0.8 Beam 6.0 cm - 3.1 envelope in 2.0 0.7 quads 0.0 1. 2. 3. 4. 5. 6. 7. 8. s (m)

Ideal bunch crossing points • 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. LLL

Injection timing Inject into crossing points Inject in between crossing points • Injection delay L/(6c) • Simultaneous injection • Kicker rise/fall time is L/(6c) -t bunch • Kicker rise/fall time is L/(3c) -t bunch 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 Decay Ring MAD-X 5.00.00 02/04/13 17.26.25 85.0 1.0 y (m) x (m) b y b x D x Lengt Gradient Aperture 81.5 0.9 D x (m), b h (m) (T/m) 1.3*√(εβ) (m) 78.0 0.8 b D 2.0 -0.34 0.207 74.5 0.7 71.0 0.6 F 2.0 0.68 0.213 67.5 0.5 Drift 10.0 - - 64.0 0.4 60.5 0.3 57.0 0.2 53.5 0.1 50.0 0.0 0.0 5. 10. 15. 20. 25. 30. 35. 40. s (m)

Injection into production straight (2) • Ensure 2cm separation Decay Ring MAD-X 5.00.00 05/04/13 15.18.45 0.6 0.0 x (m) between injected and x D x x (m) -0.1 D circulating beam at 0.5 -0.2 septum exit. 0.4 • Injected beam excursion -0.3 in kicker magnet 9.5 cm, 0.3 -0.4 in D magnet 15.2 cm. -0.5 0.2 -0.6 Length Field (T) Angle (rad) 0.1 -0.7 (m) Kicker 8.8 0.08 0.022 0.0 -0.8 0.0 5. 10. 15. 20. 25. 30. 35. 40. Septum 1.6 3.06 0.147 s (m)

Kicker design for 25 GeV muon FFAG Decay ring injection at the Table XXVIII. Parameters of the kicker system production straight Kicker total aperture (h × v) 0.3 × 0.3 m Kicker length 4.4 m requirements 1.9 µ s Rise/ fall time (5-95%) Kicker aperture 0.44 x 0.34 m Kicker max fi eld ≈ 0.1 T 0.3 µ s Rise/fall time 0.8 us Kicker pulse duration at the top Charging voltage 60 kV Difficult! Peak current in the magnet 30 kA 5.1 µ H Kicker inductance 1 Ω Kicker impedance 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) ≈ 1.25 MW Total averaged power per kicker ≈ 2.5 MW Total peak power per kicker Ω = 0 µs Ω = 120 µs = 240 µs

Injection into insertion Injecting bunches simultaneously (1) Δx • Distance of injection point from arc center Δx should be enough to allow bunch separation at end of production straights. æ ö D x = c ini + n t h dp p T o + t gap 2 t b ç ÷ è ø • 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 ν ν from end of arc.

Injection into insertion Injecting bunches simultaneously (2) • Distribution of bunch crossing points Δx 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. ν ν

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. Triplet magnet modules Matching Matching Empty to the to the arc space straight Kickers Septa

Optics of the injection straight m 20 D m 1.2 17.5 1 15 0.8 12.5 0.6 10 0.4 7.5 0.2 5 0 2.5 0 5 10 15 20 0 10 20 30 40 50 60 s m s m Dispersion matching at the end of the arc Injection insertion matched to the arc Adding one more FODO cell and changing the dipole strength (relaxing some values) Matching to the straight: work in progress...

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

Insertion • 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. τ rise/fall Angle Length Field μs (mrad) (m) (T) Septum 67.5 3.0 0.75 - Kicker 8.1 5.4 0.05 1.37

Injected beam trajectory Decay Ring MAD-X 5.00.00 10/05/13 13.07.03 0.50 x x (m) 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.0 -0.05 -0.10 0.0 10.18 20.36 30.54 40.72 50.90 s (m) 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 Kicker aperture 0.18 x 0.18 m Kicker length 5.4 m No of sub kickers 10 Rise/Fall (5-95%) 1370 ns PFNs per kicker sub units 3 Pulse duration at top 0.3 µS No of Pulse Forming Networks 30 Thyratrons 30 Travelling wave system design B field 0.06 T

Upper Arc • Dispersion suppressor at Decay Ring MAD-X 5.00.00 08/05/13 16.11.47 100. 1.4 y (m) x (m) either end of upper arc to b y b x D x 90. eliminate dispersion before 1.2 D x (m), b entering insertion. This 80. 1.0 should be further optimised. b 70. • Optics matching from 0.8 60. insertion to adjacent sections. 50. 0.6 • Matching to production 40. straight contains reverse 0.4 bend to help collimate stray 30. 0.2 electrons and muons. 20. 0.0 10. 0.0 -0.2 0.0 50. 100. 150. 200. 250. 300. s (m)

Lower Arc • There is no need for insertions in lower part of the ring. • Decay Ring MAD-X 5.00.00 09/05/13 23.19.48 The insertion contributes to the 90. 1.2 y (m) x (m) b x b y D x width of the racetrack since the 1.1 81. D x (m), b arcs bend by less than 180 1.0 72. degrees. The lower arc should be 0.9 b 63. scaled up to match this extra 0.8 width. 54. 0.7 • In order to use the same magnets 45. 0.6 as upper arc, just the drift 0.5 36. lengths are scaled up. However, 0.4 27. the focusing is adjusted by a 0.3 18. small amount to optimise the 0.2 working point. 9. 0.1 0.0 0.0 0.0 40. 80. 120. 160. s (m)

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.