# Presentation: 180051

## Linac Front end design

**Gennady Romanov**
**March 15 , 2005**

- with the help from Peter Ostroumov, Bill Foster, Doug Moehs, Ivan Gonin

- Gennady Romanov

- March 15-17, 2005

## Outline

**Ion Source**
**Radio Frequency Quadrupole RFQ**
**Medium Energy Beam Transport MEBT. **
**Room Temperature Triple Spoke Resonators section. **
**Superconducting spoke resonators sections:**
**     ****Single Spoke, Double Spoke and Triple Spoke resonators**
**Conclusions.**

- Gennady Romanov

- March 15-17, 2005

## Front end general layout

**Ion source H****-****, LEBT****	****, 0.065 MeV****	****	****                **
**Radio Frequency Quadrupole, 4-5 m, 3 MeV**
**MEBT, 2 bunchers, 4 SC solenoids, chopper, 4 m**
**RT TSR**** section, 21 resonators, 21 SC solenoid, 10 m, 15.2 Mev**
**SSR section, 16 resonators,  16 SC solenoids, 12.5 m, 33.5 MeV**
**DSR section,  28  resonators,  14  SC solenoids, 17 m, 108 MeV         **
**TSR section,   42  resonators,  42 quads, 64 m, 408 MeV**

**Frequency 325 MHz**
**Total length 112 m**

- Gennady Romanov

- March 15-17, 2005

**Notes:**
Each system deserves a separate talk. I only can give a short overview of the key issues for each them.

## Ion source

**The ion source is a multicusp, rf-driven, cesium-enhanced source of H****-****.  **
**Output energy 65 keV,  output peak current 12.7 (38) mA, pulse length 3.0 (1.0) ms, pulse rate 2.5(10) Hz  **

**  ****Design concept  - SNS**
**  ****Design issues – in general these**
**    ****sources are well understood.**
**    ****SNS ion source can be used **
**    ****for PD. Longer RF antenna**
**    ****lifetime is desirable.**
**    **

- Gennady Romanov

- March 15-17, 2005

## Toward Selecting an H- Ion Source

**The SNS Ion Source Test Bench and LEBT**

**Beam tests on the SNS RF H****-**** ion source ****(Doug Moehs)**** **
- 3.1 ms long pulse, 11.5 mA average, at 5 Hz
- The SNS routinely runs 1 ms long pulses, 30 mA at 60 Hz

**  ****Plan to test the DESY H****-**** source at 3 msec pulse length**
**                  ****in next few months**

- Gennady Romanov

- March 15-17, 2005

**Notes:**
In this picture the emittance probes have been removed from the vacuum can which is pulled back reveling the electrodes of the LEBT.
The Black cage just visible is shielding for HV and the RF coupling.
Two large HV isolation cabinets (light blue) are to the very left, in the back.

## RFQ

**RFQ accelerates H****-**** from 0.065 to 3 MeV , Ip –up to 28 mA**
** **

** ****Now RFQs are standard devices  for proton machines. There are good designs (J-PARC, SNS) and we can copy appropriate**

** ****Our additional requirement **
**for RFQ beam dynamics design**
**is ****axisymmetric ****output beam **
**to reduce halo formation in **
**MEBT and RT TSR section. (P.Ostroumov’s proposal).**

- J-PARC 30 mA RFQ

**technical solutions.**

- Gennady Romanov

- March 15-17, 2005

## RFQ

**For mechanical design the main issues will be ****1)**** Machining of big parts with high accuracy ( ****±****25 microns for vane tips) and ****2)**** The way to assemble  the RFQ body. We consider brazing (SNS approach), though the clamping with ring contacts works well too (J-PARC).**
**Currently basic RFQ parameters are found. RF design  and mechanical design are planned to be done by ANL-FNAL collaboration.**

- Gennady Romanov

- March 15-17, 2005

## MEBT

**MEBT has three main functions, i.e., matching the **
**beam from the RFQ exit plane into the MEBT chopper**
**plane, cleanup chopping, and matching the remaining**
**particles into the RT TSR section. Plus beam diagnostic.**

**SNS MEBT**

- Rebuncher

- Chopper

- Target

- Quadrupole lens

- Gennady Romanov

- March 15-17, 2005

## MEBT

**In our MEBT we have**** an axisymmetric beam ****after RFQ.**
**4 SC solenoids ****are used for focusing and matching**
**2 RT TSR ****are used as the rebunchers**
**One chopper**
**This is conceptual design. The detailed design is still ahead. **

- SC solenoid

- RT TSR

- TRACK simulation

- Gennady Romanov

- March 15-17, 2005

## MEBT

**The MEBT installed at KEK.**

- Gennady Romanov

- March 15-17, 2005

## RT TSR section

_**Why this room temperature section?**_
**Beam dynamics at low beta demands adiabatic acceleration, smooth transition from RFQ to SC sections which have high accelerating rate. **
**That means:**
**    ****- variable beta accelerating lattice - gaps and dis-tances between them change with particle velocity**
**    ****- focusing period should be as short as possible **
**    ****- smooth increasing of accelerating rate**
** ****It is expensive and difficult to design and produce beta variable SC cavities. This is not a problem for RT cavities**

- Gennady Romanov

- March 15-17, 2005

## RT TSR section

**Our solution is Room Temperature Triple Spoke Resonator  (aka Cross-bar H-type resonators) section from 3 MeV to 15 MeV .**

- Gennady Romanov

- March 15-17, 2005

## RT TSR section

**The main advantage of RT TSR is its high shunt impedance. **

**For 3-15 MeV losses in copper:**
**DTL – 1.06 MW**
**RT TSR – 0.4 MW**
**Diameter of resonator**
**DTL, SDTL – 70 cm**
**RT TSR – 40 cm**
**RT TSR should be cheaper**

- RT TSR

- SDTL (J-PARC)

- DTL (J-PARC)

- Gennady Romanov

- March 15-17, 2005

## RT TSR section

**SC solenoids in individual cryostats are to be used to maintain axisymmetric focusing **
**Common vacuum tank with integrated RT TSR and SC solenoids seems to be effective mechanical design.**

**Helps to keep**
**period short.**
**End walls of cavity**
**are unstressed.**

- SC solenoid in individual cryostat

- Gennady Romanov

- March 15-17, 2005

## RT TSR section

- Cold  model of CH resonator (Frankfurt).

- SC quadrupole lens in
- individual cryostat (Berkley)

**There no prototypes of RT TSR and  SC solenoids that meet our **
**requirements , but we can find similar efforts elsewhere**

- Gennady Romanov

- March 15-17, 2005

## RT TSR section

_**Past results:**_** **
** ****RF parameters are defined for all  RT TSR. The fields are simulated and used in 3D beam dynamic study**
**  ****Preliminary design of SC solenoids has been done and feasibility confirmed (Y.Terechkine)**
_**Plans: **_
** ****RT TSR optimization, couplers and mechanical design**
** ****SC solenoid design**
** ****Vacuum tank design**

- Gennady Romanov

- March 15-17, 2005

## SC Spoke Resonator sections

**SC Spoke Resonator sections provide acceleration**
**from 15 MeV up to 400 MeV.**
**We study and optimize all three types of resonators**

**Successful power tests are done for all SR (ANL, LANL, ORSAY).**
**So, we are optimistic about performance of these resonators.**

- Gennady Romanov

- March 15-17, 2005

## SC Spoke Resonator section

_**What is done:**_** **
** ****RF simulations are done for all cavities and fields are used in 3D beam dynamic study**
** ****Optimization of cavity shapes is in progress**
** ****HOM study has been started for TSR**
_**Plans: **_
** ****Further RF optimization of SR designs**
** ****Development of universal power coupler design**
** ****Mechanical design **
** ****Design of SC solenoid and quadrupole lens for this section**

- Gennady Romanov

- March 15-17, 2005

## CONCLUSIONS

**PD Front End is technically feasible**
**    ****- ****SNS and J-PARC machines are built**
**    ****- ****HIPPI project works in the same direction and  has made a good progress**** **
**No reasons to expect  high cost of Front End**
**Based on existing machines, we estimate risk of building PD Front End to be from low to moderate.**
**We developed short and long term plans of work, they contain R&D issues mentioned above.**

- Gennady Romanov

- March 15-17, 2005