# Presentation: 250906

## RF Systems for NSLS-IIJ. Rose,  A. Blednykh,  N. Towne

- Booster
- IR
- Linac
- Harmonic RF

**RF Systems for NSLS-II****J. Rose,  A. Blednykh,  N. Towne**

- With help from many others at BNL and other institutions

## X-RAY Ring RF requirements

| Beam Energy | 3 GeV |
| --- | --- |
| Beam Current | 500 mA |
| Energy loss/turn | 2 MeV |
| p/p acceptance | 3 % |
| Power to Beam | 1 MW |

**X-RAY Ring RF requirements**

| RF parameters |  |
| --- | --- |
| Frequency | 500MHz |
| Cavity Voltage | 4.9 MV |
| Momentum
compaction | 0.00035 |
| Synchrotron
frequency | ~35kHz |

## Baseline CESR-B Cavity

**SCRF chosen for lower R/Q,  highly**
**damped HOM’s, lower operating**
**cost and comparable capital cost **
**CESR-B has well established commercial **
**production. Units 15 and 16 **
**now being produced by ACCEL.**
**In operations at Cornell (4), CLS(2), **
**Taiwan (2). Being commissioned at**
**Diamond (3). Ordered for ASP(?)**

## Harmonic Cavity for Bunch Lengthening

**Harmonic Cavity for Bunch Lengthening**

- 4.9MV @500MHz required for 3%
- Momentum acceptance: 1.6MV @
- 1500MHz requires 3 cavities

- Work continues on effect of bunch train
- transients on bunch lengthening

- N. Towne

## X-Ray Ring Layout

** ****4 - 500 MHz cavities **
- (1MW req’d and 250kW/coupler)
** ****3- 1500 MHz cavities **
- (4.5MV @500MHz=1.5MV At 1500MHz and 0.5MV/cav)

- Stray magnetic fields at cavities must be << 0.5 Gauss at cooldown !

## IR Ring Requirements

- Vacc >2.5MV
- Beam current =1.0A (1.5)
- Beam power   <10 kW

**1 SCRF module**
- (1M$ cavity, 0.2M$ RF
- + >120W @4.5k cryoplant)

- Low beam power means either matching stubs
- or adjustable coupling
- Benefits from Antennae Coupler !

**Fwd. and Rev. Power vs. I**

## RF Power Source Options

- costed, one per cavity
- @ 2.3M$ ea
- CPI 800 kW klystron exists
- if dual or high power coupler
- adopted (can be optimized for 600kW)
-  Option: Combine 50 kW IOT’s from broadcast industry (times 6 or 12 does not seem attractive,will study Diamond’s results)
- Will use IOT’s for Booster, IR ring

**RF Power Source Options**

- TH2161B installed at CLS

## Booster Ring Requirements

**Booster Ring**** ****Requirements**

- Energy loss per turn = 1MeV, Vacc = 2MeV for
- 0.9% RF acceptance
- Negligible Energy gain per turn ~29 keV for 300ms ramp
- Beam current = ~3mA (~6mA for IR) Beam power 3-6 kW

-  2 “Petra” type cavities and 2 -50kW IOT’s
- (1.5M$ cavities + 0.4M$ RF)
-  OR 1 SCRF module + 1 -50kW IOT
- (1M$ cavity, 0.2M$ RF
- + >92W @4.5k cryoplant)

## Cavity Modeling with GdFdl

- GdfidL vs. CFISH
- Benchmark ferrite losses,
- superconductor surface
- resistance
- GdfidL vs. measurements
- Confirm ferrite properties
- Full Cavity results are now
- being calculated to be used
- to analyze CB instability
- Next is coupler analysis,
- Cavity pair with spool piece

- Alexei Blednykh

## R&D roadmap for power coupler

- Reduces # X-ray cavities from 4 >2
- which reduces ring impedance
- Adjustable coupling to minimize
- IR ring, Booster rf power req’d.
- Lower static cryo-losses
- Frees up 6m straight !

**R&D roadmap for power coupler**

- R&D needs:
- RF transmitter
- Coupler development
- Coupler test stand
- Cryo-test facility
- Cavity prototype

**FOR NSLS-II:  Dual antennae coupler design most appealing !**
**250kW/coupler has been demonstrated, 500kW/cavity low technical **
**risk.**
**Adjustable coupling allows better matching for low power **
**requirements of Booster, IR rings: need only one coupler: lower cost**
**Road to upgrade: Add HOM to IR ring 2nd coupler port? **

## Cryo-Plant Requirements

| X-ray -4.9MV | 4 Cavities | 2 cavities |
| --- | --- | --- |
| Cavity V | 1.23 MV | 2.45 MV |
| Static load | 30W  ea | 30W ea |
| Dynamic load | 26 W ea | 98 W ea |
| Valve box | ~30W* total | ~30W * total |
| Harmonic cav. | 3 @ 15 W | 3@15 W |
| +1W/m transfer lines | 100  W * | 75  W* |
| IR Ring | (30Static +98Dynm.+30VB) W |  |
| Booster | (30Static +62Dynm.+30VB) W |  |
| Total | 679 W @ 4.5K | 686 W @ 4.5K |

- * Not sure how many VB’s needed, how many meters of transfer line

## 2.998 GHz Linac

- Length 		5.2 m
- Shunt imp.	51 M/m
- Q			14000
- Filling time		0.74 s
- Energy gain 	12.6*sqrt(PMW )
- Attenuation  = 0.55 Np

**2.998 GHz Linac**

- Picture courtesy of ACCEL

- Energy gain 80MeV/tank for 40MW power input (no-load)
- 1 Klystron TH2100 (45MW) per accelerating tank
- Solid state modulator to drive klystron

## Low Level RF

- Emphasis to date has been on cavity choices and
- high power systems which have immediate impact on
- beam dynamics, ring layout, and have longer lead times.
- Unlike the cavities and high power systems the LLRF is
- likely to be upgraded throughout the life of the project.
- Take advantage of the flexibilty of new digital RF
- systems and direct IQ modulation at 500 and 2998MHz.
- Unlike the high power systems LLRF is not available
- commercially, and skills need to be in-house. Digital
- RF requires additional skill set (e.g., the rf programmer)

## Conclusions

- RF requirements for NSLS-II can be met with existing
- technology, often from commercial sources
- Development of high power and/or dual antennae coupler
- would reduce number of cavities from 4 to 2 in X-ray ring,
- reducing impedance, freeing up ID straight. Allows more
- efficient low power operation in Booster, IR rings.
- Upgradeable,  not locked in to existing performance.
- Need to continue work on cavity modeling and impedance
- calculations,  analysis of bunch lengthening with harmonic
- RF in the near term, and later on systems analysis and LLRF