# Presentation: 660458

## SPL-based Proton Driver for Facilities at CERN:Updated Description

**R. Garoby, F. Gerigk and the SPL study group**
**ISS meeting, 25-28.4.06**

## SPL block diagram (CRD-2)

**SPL (beam in 2015 ?)**

-  relocation of Linac4, adding 366 m of SC RF,
-  PS booster becomes obsolete,
-  cavity power < 1 MW,
-  TESLA/ILC type cryostats (INFN Milano) with
-     5-cell SC Nb cavities (CEA/INFN) and cold
-     quadrupoles,
-  layout and beam dynamics (CEA Saclay).

**SPL block diagram (CRD-2)**

## SPL layout (CDR-2)

**SPL layout (CDR-2)**

## Beam dynamics (CEA Saclay)

- phase advance per metre

- emittance evolution

- beam envelopes

- output phase space

**SPL beam dynamics (CDR-2)**

## SPL beam characteristics

|  | CDR1
[2000] | CDR2
[2006] |  |
| --- | --- | --- | --- |
| energy | 2.2 | 3.5  | GeV |
| average beam power | 4  | 4 | MW |
| length | 690 | 450 | m |
| average RF power | 24 | 17.4 | MW |
| average cryogenics power | 9.6 | 6.7 | MW |
| repetition rate | 50 | 50 | Hz |
| beam pulse length | 2.8 | 0.57 | ms |
| average pulse current* | 13 | 40 | mA |
| peak current* | 20.8 | 64 | mA |
| beam duty cycle | 14 | 2.9 | % |
| peak RF power | 32 | 163 | MW |
| no. of 352.2 MHz klystrons (1 MW) | 44 | 14 |  |
| no. of 704.4 MHz klystrons (5 MW) | - | 44 |  |
| no. of tetrodes | 79 | 3 |  |
| cryo temperature | 4.5 | 2 | K |

- * after chopping

**SPL beam characteristics**

## Scenarios for accumulation & compression (1/7)

**- for a**** beta-beam based**** ****facility**
** ****[****200 kW beam @ 1-5 GeV****]**
**+**
**super-beam [****4 MW @ 3.5 GeV****]**

**Long beam burst (~ms)**
**********direct use of linac beam**

**- for a**** ******** factory**** [****4 MW beam @ 4-10 GeV****]**

**Short beam burst (~********s)**
**********accumulator**

**Short beam burst (~********s)**
**********accumulator**
**+**
**Short bunches (~ns)**
**********compressor**

- For  physics, the time structure of the linac beam has to be changed:

- The requirements of a  factory are the most demanding.

## Scenarios for accumulation & compression (2/7)

| Beam power (P) | ~ 4 MW |
| --- | --- |
| Kinetic energy (T) | 4 – 10 GeV |
| Bunch length | 1-3 ns rms |
| Distance between bunches ??? | 100 ns |
| Burst length | 1-3 s |
| Repetition rate | 50 Hz |

- Parameters required by a  factory*

*** Partial understanding...**

## Scenarios for accumulation & compression (3/7)

- Consequences for a linac-based driver

| Kinetic energy (T) | Cost increases with T
 Minimize T (< 4 – 8 ? GeV) |
| --- | --- |
| Repetition rate (frep) | Constant beam power imposes the number of protons/pulse Np |
| Bunch length (lb) | Energy acceptance + longitudinal space charge restrict to low longitudinal emittance
 minimum number of bunches (Nb) |
| Distance between bunches (db) | Accumulator circumference C is proportional to Nb  db & Laslett tune shift Q is proportional to C
 minimize db to minimize Q & cost |
| Burst length | Constraints the highest value of C |

## Scenarios for accumulation & compression (4/7)

**Scenarios for accumulation & compression (4/7)**

- With SPL CDR1 (2000): severe constraint due to the low beam energy

| T | 2.2 Gev |
| --- | --- |
| frep | 50 Hz |
| Np | 2.27 1014 |
| lb | 1 ns |
| Nb | 140 |
| db | 22.7 ns |
| C | 3.316 s |

## Scenarios for accumulation & compression (5/7)

- With SPL CDR2 (2006): higher beam energy => less constraints

| Kinetic energy (T) | 3.5 GeV |
| --- | --- |
| Repetition rate (frep) | 50 Hz  Np= 1.43 1014 p/p |
| Bunch length (lb) | For the same p/p acceptance + because of lower Np 
+ relaxing on lb (2 ns instead of 1 ns)
 Nb (goal) = 17
[8.41 1012 p/b] |
| Distance between bunches (db) | db (goal) = 90.86 ns
C (goal) = 1.635 s |

- First approach...

- Feasibility in the accumulator/compressor has been pre-checked

## Scenarios for accumulation & compression (6/7)

**With a linac-based driver there is the possibility to do multiple accumulations with a single linac beam pulse, and therefore generate multiple bursts of beam onto the target.**
- This is of interest if:
-  all parameters are constant in the  channel during the whole duration of the proton beam on the target (transverse focusing, gradient in the RF cavities...). It is not unreasonable to hope for ~ 1 ms.
-  the  storage ring is long enough to contain all the successive bursts.
- The main disadvantage is that the kickers must provide multiple kicks within ~ 1 ms.
**This makes it possible to tailor the intensity per burst / the distance between bunches / the main cycling rate of whole facility...**

## Scenarios for accumulation & compression (7/7)

- With SPL CDR2 (2006): other approach using multi-pulsing

| Kinetic energy (T) |  > 3.5 GeV | 3.5 GeV |
| --- | --- | --- |
| Repetition rate (frep) | 6 bunches at 50 Hz | 12 bunches at 25 Hz |
| Number of protons/bunch | 2.4 1013 p/p | 2.4 1013 p/p |
| Time interval between bunches | 95 s | 95 s |
| Total burst duration | 475 s | 1.045 ms |
| Bunch length (lb) | ~ 3 ns ? | ~ 3 ns ? |

**Fill & eject 6 times single**
**bunches from an**
**accumulator/compressor**
**of 272 ns revolution period**

**Fill & eject 12 times single**
**bunches from an**
**accumulator/compressor**
**of 272 ns revolution period**

**Many open questions to be studied ...**

## The new SPL design (CDR2 – 2006) is largely improved:

energy (3.5 GeV) is a compromise that can potentially satisfy EURISOL, neutrino applications, and LHC upgrade scenarios,
design is more optimum (length reduced by 35% while the  energy is increased by 60%, higher instantaneous current reducing the number of turns for accumulation in the ring...)
upgrades are possible in terms of energy and/or power.

This typically illustrates the potential of a linac-based proton driver for a  factory, which can be the basis of a high energy accelerator complex [®] and has a remarkable flexibility to adapt to the requirements of the following part of the facility.

- energy (3.5 GeV) is a compromise that can potentially satisfy EURISOL, neutrino applications, and LHC upgrade scenarios,
- design is more optimum (length reduced by 35% while the  energy is increased by 60%, higher instantaneous current reducing the number of turns for accumulation in the ring...)
- upgrades are possible in terms of energy and/or power.
**This typically illustrates the potential of a linac-based proton driver for a ******** factory, which can be the basis of a high energy accelerator complex **_[[](slide15.xml)__[®](slide15.xml)__[]](slide15.xml)_** ****and has a remarkable flexibility to adapt to the requirements of the following part of the facility.**

**Conclusions & outlook**

## ANNEX

## Evolution of the CERN accelerator complex 

**SPL’**
**RCPSB**

**SPS**

**SPS+**

**Linac4**

**SPL**

**PS**

**LHC**

**DLHC**

- Output energy

**160 MeV**

**1.4 GeV**

**~ 5 GeV**

**26 GeV**

**40 – 60 GeV**

**450 GeV**

**1 TeV**

**7 TeV**

**~ 14 TeV**

**Linac2**

**50 MeV**

**SPL: **Superconducting Proton Linac (~ 5 GeV)
**SPL’: **RCPSB injector
- 	(0.16 to 0.4-1 GeV)
**RCPSB: **Rapid Cycling PSB
- 	(0.4-1 to ~ 5 GeV)
**PS2:** High Energy PS
- 	(~ 5 to 50 GeV – 0.3 Hz)
**PS2+:** Superconducting PS
- 	(~ 5 to 50 GeV – 0.3 Hz)
**SPS+: **Superconducting SPS
- 	(50 to1000 GeV)
**DLHC**: “Double energy” LHC
- 	(1 to ~14 TeV)

- Proton flux / Beam power

**Evolution of the CERN accelerator complex **

**PS2 (PS2+)**

## Scenarios for the proton accelerator complex- Stages of implementation

| STAGE | 1 | 2 | 3 | 4 |
| --- | --- | --- | --- | --- |
| DESCRIPTION (new accelerator) | Linac4
PSB
PS
SPS | Linac4
PSB
PS2 or PS2+
(& PS)
SPS | Linac4
SPL
PS2 or PS2+
SPS | Linac4
SPL
PS2 or PS2+
SPS+ |
| Performance of LHC injectors (SLHC) | +
Ultimate beam from PS | ++
Ultimate beam from SPS | ++
Maximum SPS performance | +++
Highest performance LHC injector |
| Higher energy LHC | - | - | - | +++ |
| beam | - | - | ++ (~100) | ++ (~200) |
| Factory | - | - | +++ (~5 GeV prod. beam) | +++ (~5 GeV prod. beam) |
| k,  | - | ~150 kW beam at
50 GeV | ~200 kW beam at
50 GeV | ~200 kW beam at
50 GeV |
| EURISOL | - | - | +++ | +++ |

## Exotic scenarios for accumulation & compression

- With SPL CDR2 (2006): other approach using multi-pulsing

| Kinetic energy (T) |  > 3.5 GeV | 3.5 GeV |
| --- | --- | --- |
| Repetition rate (frep) | 6 batches of 3 bunches
at 50 Hz | 12 batches of 3 bunches
at 25 Hz |
| Number of protons/bunch | 2.4 1013 p/p | 2.4 1013 p/p |
| Time interval between bunches | 95 s | 95 s |
| Total burst duration | 475 s | 1.045 ms |
| Bunch length (lb) | ~ 2 ns ? | ~ 2 ns |

**Fill & eject 6 times multiple**
**bunches from an**
**accumulator/compressor**
**of 272 ns revolution period**

**Fill & eject 12 times multiple**
**bunches from an**
**accumulator/compressor**
**of 272 ns revoluton period**

_**Main issue**_**: the distance between bunches imposes a quantum ********f in the**
****** ****capture & bunch rotation channel. How much is acceptable ? 10 MHz ?**