# Presentation: 667834

## Progress on Linacs and RLAs for the IDS Baseline  

- Progress on Linacs and RLAs for the IDS Baseline _** **_

## Neutrino Factory – ISS/IDS Baseline

## Acceleration Scenario – ISS/IDS Baseline

- Linear Pre-accelerator (244 MeV to 900 MeV)
- RLA I   4.5 pass, **0.6 GeV/pass**, (0.9 GeV to 3.6 GeV )
- RLA II   4.5 pass, **2 GeV/pass** (3.6 GeV to 12.6 GeV  )
- Non scaling FFAG (12.6 GeV to 25 GeV )

## Acceleration Scheme – IDS Goals

**Engineering design foundation**
- Define beamlines/lattices for all components
- Design lattices for transfer lines between the components
- Resolve physical interferences, beamline crossings etc  **Floor Coordinates**
- Carry out end-to-end tracking study  **Machine Acceptance**
- Engineer individual active elements (magnets and RF cryo modules)

## Towards Engineering Design Foundation 

- Towards Engineering Design Foundation** **

## Arcs ‘Crossing’ - Vertical  Bypass

## Initial beam emittance after the cooling at 220 MeV/c 

| ISS/IDS |  | rms | A = (2.5)2  |
| --- | --- | --- | --- |
| normalized emittance: x/y  | mmrad  | 4.8 | 30 |
| longitudinal emittance: l 
lp z/mc)
     momentum spread: p/p 
     bunch length: z | mm 

mm | 27

0.07
176 | 150

0.17
442  |

## Pre-accelerator  different style cryo-modules

|  | Short | Medium | Long |
| --- | --- | --- | --- |
| Number of periods | 6 | 8 | 11 |
| Total length of one period | 3 m | 5 m | 8 m |
| Number of cavities per period | 1 | 1 | 2 |
| Number of cells per cavity | 1 | 2 | 2 |
| Cavity accelerating gradient  | 15 MV/m | 17 MV/m | 17 MV/m |
| Real-estate gradient  | 3.72 MV/m | 5.06 MV/m | 6.33 MV/m |
| Aperture in cavities (2a) | 460 mm | 460 mm | 460 mm |
| Aperture in solenoids (2a) | 460 mm | 460 mm | 460 mm |
| Solenoid length | 1 m | 1 m | 1 m |
| Solenoid maximum field | 1.1 T | 1.4 T | 2.5 T |

## Linear Pre-accelerator – 244 MeV to 909 MeV 

- 6 short cryos

- 8 medium cryos

- 11 long cryos

## Introduction of synchrotron motion in the linac

- Longitudinal acceptance: p/p=0.17 or =93 (200MHz)

## Linear Pre-accelerator – Longitudinal dynamics 

**Linear Pre-accelerator – Longitudinal dynamics**** **

**Transverse acceptance** (normalized) : TA = (2.5)2= 30 mm rad

**Longitudinal acceptance**: LA = (2.5)2 pz/mc= 150 mm

## Injection double-chicane

********

********

## Pre-accelerator–Chicane–Linac Matching

## RLA I Linac – Longitudinal Dynamics

- = 2×10-5

## Linear Pre-accelerator + RLA complex

**Linear Pre-accelerator + RLA complex**

##  RLA requirements 

-  Simultaneous acceleration of both + - species
-  Manageable orbit separation at recirculation arcs
-  Beam dynamics challenges  RLA Optics solutions_** **_
-  Phase slippage in the linacs
-  Multi-pass linac optics
-  Orbit separation – linac ends
-  Droplet return arc – compact lattice design

**‘****Dogbone’ RLA with FODO Focusing**

## RLAs for Muon Acceleration

**‘****Dogbone’** (Single Linac) RLA has advantages over the Double-Linac RLA ‘Racetrack’
- better orbit separation at linac’s end ~ energy difference between consecutive passes (2E)
- allows both charges to traverse the Linac in the same direction (more uniform focusing profile
- the droplets can be reduced in size according to the required energy
-  **FODO** Optics is superior to Triplet focusing  more passes are possible with the FODO scheme

## Phase slippage of a semi-relativistic muon beam injected with the initial energy E0 and accelerated by E in a linac of length, L   assuming uniformly spaced RF cavities phased for a speed-of-light particle

The injection energy, E0 , needs to be chosen, so that a tolerable level of the RF phases slippage along the main linac can be maintained (~40 deg). 

- The injection energy, **E****0** , needs to be chosen, so that a tolerable level of the RF phases slippage along the main linac can be maintained (~40 deg).

**Phase slippage in the linac**** **

## Phase slippage in the RLA linac

- RF phase slippage along the multi-pass linacs; initial **‘gang phases’** for each pass were chosen for the optimum longitudinal bunch compression in each linac-Arc segment

- RLA I (0.6 GeV/pass)

- RLA II (2 GeV/pass)

## The focusing profile along the linac (quadrupole gradients) need to be set so that one can transport multiple pass beams within a vast energy range (provide adequate transverse focusing for given aperture) . 
The beam is traversing the linac in both directions   one chooses a ‘flat focusing profile’ (Bob Palmer) for the entire linac: e.g. the quads in all cells are set to the same gradient, corresponding to 90 deg. phase advance per cell determined for the lowest energy (injection) – no quad scaling with energy
The requirement of simultaneous acceleration of both ± species imposes mirror symmetry of the ‘droplet’ Arcs optics (the two species move in the opposite directions through the Arcs). This in turn puts a constraint on the exit/entrance Twiss functions for the two consecutive linac passes: 
outn = inn+1  and  outn = -inn+1             where n = 0, 1, 2.. is the pass index

- The beam is traversing the linac in both directions   one chooses a **‘flat focusing profile’** (Bob Palmer) for the entire linac: e.g. the quads in all cells are set to the same gradient, corresponding to 90 deg. phase advance per cell determined for the lowest energy (injection) – no quad scaling with energy
- The requirement of simultaneous acceleration of both ± species imposes **mirror symmetry** of the ‘droplet’ Arcs optics (the two species move in the opposite directions through the Arcs). This in turn puts a constraint on the exit/entrance Twiss functions for the two consecutive linac passes:
- outn = inn+1  and  outn = -inn+1             where n = 0, 1, 2.. is the pass index

**Multi-pass Linac Optics**

## FODO - ‘flat focusing' linac profile

**FODO - ‘flat focusing' linac profile**

- 1-pass, 1250-1800 MeV

- ‘half pass’ , 900-1200 MeV

- initial phase adv/cell 90 deg – fixed gradient in all cells (no scaling with energy)

- phase adv. diminish uniformly in both planes

- Linac cryo-module – solenoid replaced with a quad

## FODO - ‘flat focusing' linac profile

**FODO - ‘flat focusing' linac profile**

- 2-pass, 1800-2400 MeV

- 3-pass, 2400-3000 MeV

- phase adv. diminish uniformly in both planes

## FODO - ‘flat focusing' linac profile

- 4-pass, 3000-3600 MeV

- phase adv. still  larger then 180 deg.  in both planes

## Mirror-symmetric ‘Droplet’ Arc  –  Optics  

- 16 cells

- 2 cells

- 2 cells

- (out = in ,and out = -in , matched to the linacs)

## Summary

- IDS Goals – laying **engineering design foundation**
- Define beamlines/lattices for all components
- Design lattices for transfer lines between the components
- Resolve physical interferences, beamline crossings etc  Floor Coordinates
- Carry out end-to-end tracking study  Machine Acceptance
- Implementing chromatic corrections with sextupoles
- Engineer individual active elements (magnets and RF cryo modules)
- Element count and costing