# Presentation: 475347

## Status of the RT CH-DTL Development and Beam Dynamics Layout of the GSI Proton Linac

- R.Tiede
- HIPPI Annual Meeting (WP2),
- Frankfurt, September 29 - October 1, 2004

- Brief description of CH resonatorsand of the ‘KONUS’ beam dynamics
- GSI Proton Linac beam dynamics design status
- CH-DTL cavity design status
- Outlook / Conclusions

## H-mode Structure Family

_**H-mode Structure Family**_

- HSI – IH DTL , 36 MHz

- HSI – IH RFQ 1, 36 MHz

## ‘KONUS’ Beam Dynamics(Kombinierte Null-Grad Struktur = Combined Zero Degree Structure)

- KONUS illustrated on the GSI HLI – IH structure :

## Efficiency of H-Mode Structures

- Smaller power loss due to transverse current flow on cavity walls.
- Higher gradients, due to slim drift tubes (without focusing elements inside).
- KONUS Dynamics :
- Less rf gap defocusing (0° synchronous phase).
- Longer lens free sections –high overall accel. elements density.

_**Efficiency of H-Mode Structures**_

## GSI  Proton Linac - Design Parameters 

## GSI  Proton Linac – Overall Layout(all Accelerator Structures Operated at 352 MHz)

- Frankfurt Proposal for a 4-Rod, 352 MHz RFQ

- Design of Multigap CH-Cavities with MWSTM

## GSI  Proton Linac – CH DTL Section

_**GSI  Proton Linac – CH DTL Section**_

## GSI  Proton Linac – Frontend Design

- Two options were investigated :
- Long CH-DTL with integrated
- 	quadrupole triplets
- Compact
- Fewer elements
- More effective utilization of power supply (up to 1 MW)
- Separated CH-DTL without internal
- 	lenses, MEBT section
- More flexible for variable beamparameters out of the RFQ
- More ‘tuning knobs’
- Easier construction and resonancetuning of ‘short’ CH-DTL’s

**W****out ****= 9 MeV**

**W****out ****= 10.4 MeV**

## Beam Dynamics Design of the MEBT and DTL Frontend

_**Beam Dynamics Design of the **__**MEBT and DTL Frontend**_

## Beam Dynamics Design – Next Steps

- Beam dynamics design of the GSI Proton Linac for the FAIR facility is completed with respect to the fixing of the basic parameters (number of tanks, choice of the frontend option).This gives safety for the CH-DTL structure design and construction.
- However, the design of the *3 – 70 MeV* CH-DTL section in detail is an
- ongoing process.
- Attention is especially focused on:
- Definition of the desired RFQ output distributions (absolute values and orientation in phase space) in close cooperation with the RFQ designers and optimization of the MEBT section.
- Reduction of emittance growth along the DTL. Possibly well-defined particle loss by using scrapers, with the aim to deliver *70 mA* protons (out of max. *90 mA*) within the emittances required for the multiturn SIS injection.
- The completed beam dynamics design will be part of the GSI Proton Linac
- Technical Report (first draft scheduled mid Oct. ’04, final version sched. Jan. ’05).

## CH-DTL : Early Design(Influenced by IH-DTL Design Experience)

- Vane undercuts (‘magnetic flux inducer’)

- Wide vanes, short stems

## Cavity (Cross Section) Design with Microwave StudioTM for Shunt Impedance Optimization

_**Cavity (**__**Cross Section**__**) Design with **__**Microwave StudioTM for Shunt Impedance Optimization**_

- Cavity cross section optimisation based on single cells performed.
- Effective shunt impedances ranging from 100 M/m at injection energy down to 35 M/m at the linac exit seem feasible.
- Main result : “slim” stems in cross sectional plane are favourable.

## Early Mechanical Design Draft 

- Further results of the cavity cross section
- and multicell optimization were :
- No vane undercuts necessary.
- Vanes are narrow (unlike for the sc prototype cavity and the existing model). Even a direct connection of the stems to the cavity wall is possible.
- The existing 352 MHz, 1:1 scale model cannot be used for “cold” model measurements :

## Status of the Planned “Cold” Model Measurements

- A cold model was foreseen in the case of a sophisticated, long cavity with integrated triplets, to gain safety for the prototype cavity design data.
- There was a hope to reuse the main part of the existing sc CH model, as the project budget is quite tight.
- Meanwhile the design of the room temperature CH is quite different from the existing model. Besides, for a shorter cavity without integrated lenses one can trust simulation, as shown below. This is why the **rf measurements for cavity frequency and flatness tuning will be done directly on the prototype cavity!**

**Measurements on the sc CH model cavity**

## Cavity (Cross Section) Design with Microwave StudioTM for Low Energies (Front End)

_**Cavity (**__**Cross Section**__**) Design with **__**Microwave StudioTM **__**for Low Energies**__** (Front End)**_

- Comparison of present design (optimized for **5 MeV**) with former design status (opt. for **50 MeV**) :

**Courtesy of G. Clemente**

**Courtesy of Z. Li**

## Influence of Cross Section Parameters on Shunt Impedance

_**Influence of Cross Section Parameters**__** on Shunt Impedance**_

## Cavity Construction Options (1)

- During the design procedure, **3 basic options** for the mechanical realization of the room temp. CH cavity were considered:
- Option :This was deduced from the IH – DTL design experience. The stems are made of massive copper and screwed to the vanes (the alignment is provided by a notch bar). Stems can be moved for longitudinal adjustment. Cooling is done by heat conduction.

**Courtesy of G. Hausen**

## Cavity Construction Options (2)

_**Cavity Construction Options (**__**2**__**)**_

- Option :Stainless steel stems are fixed (welded to the vanes) and equipped with water cooling chanels (after fabrication, the whole tank and stem array is copper plated in common). The alignment precision is provided by a central bore. Massive copper inserts containing the drift tube are press-fitted into the precision bore.

## Cavity Construction Options (3)

- Option :There is a one-stem construction traversing through the tank cross section. Thereby water flow is more effective. Water can pass nearby the drift tube, by a surrounding  ring. The massive copper drift tube (made of two parts) is inserted to the ring element and press-fitted.

**Courtesy of K. Dermati (GSI)**

## Mechanical Stress Study for Design Option 2

_**Simulated and Experimental Result**_

**Courtesy of K. Dermati (GSI)**

## Results of the Design and Fabrication Study Commissioned to an Industrial Manufacturer *) 

_**Results of the Design and Fabrication Study Commissioned to an Industrial Manufacturer **__***) **_

***)****	****“Neue Technologien” (NTG)**** , Gelnhausen, Germany**
**	****Results of the design study will be denoted by using the company logo : **

- Based on the preparatory design works, a design and fabrication study has been ordered from an industrial manufacturer.
- The study has been completed and delivered to IAP on 21.9.2004.
- The study compares different construction options and offers possible mechanical realizations and solutions for machining techniques. Finally a preferred design solution is worked out.
- Based on the results of the study, the construction of the CH prototype cavity can be started.
- 	The study itself is not imply any detailed (based on exact cavity parameters) CH prototype cavity construction!

## Design and Fabrication Study : Drift Tube Design Options 

- Two massive copper half drift tubes attached to the stem by press-fit

- Alternative for long tubes

- Massive copper drift tube soldered to the stem

## Design and Fabrication Study : Stem Design Options 

_**Design and Fabrication Study : **__**Stem Design Options **_

- Circular cross section : simple fabrication

- Rectangular cross section: shape can be fitted for the whole energy range

## Design and Fabrication Study : Assembly Options 

_**Design and Fabrication Study : **__**Assembly Options **_

- Three alternatives with stems attached directly to the tank, without vanes

- Further alternatives: stems connected to vanes ; segmented cell structure

## Design and Fabrication Study : Favoured Option 

- Low energy part option

- High energy part option

## Project Team

_**GSI**_

- L. Groening
- W. Barth
- K. Dermati

_**IAP**_

- U. Ratzinger (WP2, WP3, WP5)
- R. Tiede (WP2, WP5) H. Podlech (WP3)
- G. Clemente (WP2)
- J.Dietrich (WP5, HIPPI additional staff)
- H.Höltermann (WP5, HIPPI additional staff)
- A. Sauer (WP3, WP5, HIPPI additional staff)

_**GUESTS**_

- Z. Li (Lanzhou, GSI, IAP)
- S. Minaev (ITEP, IAP)

_**IAP **__**Workshop and other permanent staff:**_
- In total up to 10 additional project co-workers

## Outlook / Conclusions

- The design work on the beam dynamics layout for the GSI Proton Linac is almost finished. The design status will be published soon as a part of a GSI Technical Report.
- The preparatory work for starting the prototype cavity design is completed. Some “highlights” are :
- 	• 	Cavity design optimization with Microwave StudioTM.
- 	• 	In-house development of concepts for technical design alternatives.
- 	• 	Mechanical stress study – GSI contribution (doctoral thesis).
- 	• 	Preparation of a design and fabrication study by industry.
- We have hired 3 additional staff members (doctoral candidates; post doc) by means of the HIPPI financial support. Another doctorand with non-HIPPI financial support is working exclusively for HIPPI WP2.
- Thank you for your attention !