High performance niobium cavities

Ganapati Myneni

Jefferson Lab, University of Virginia

and Virginia Tech

1st International Workshop on Accelerator-Driven Sub-Critical Systems & Thorium Utilization

September 27-29, 2010

Motivation

• ��Specifications of the e-LINAC• ��Specifications of the e-LINAC~ 25 MV/m, high Q and CW ingot niobium cavities

• Demonstrate high performance ingot niobium technology

• ADS training/teaching facility

http://conferences.jlab.org/sstin/index.htmlhttp://www.phys.virginia.edu/Announcements/LinacWorkshop/agenda.html

Birth of Ingot Niobium Technology CBMM/RMCI-JLab CRADA, August 2004

Comparison of Single and Poly Crystal RRR niobium

1000

1200

600

800

1000

oad

(Pou

nds)

Poly Crystal

Single Crystal

0

200

400

0 20 40 60 80 100 120

LoSeptember 2004

Percentage of elongatioon

Chosen for Excellent Ductility and Surface Smoothness with just BCPFirst CBMM/JLab International Patents were applied for inFirst CBMM/JLab International Patents were applied for in

April, 2005

Heat Treatment Temperature Study on Single-Cell

1E+10

0

T=1.7K

1E+10

0

T=2.0K

“Ningxia” LG Nb, 1470 MHz

1E+09

Q0

Baseline (BCP)

800C/3h, 400C/20min, 120C/12h

1E+09

Q0

Baseline (BCP) 1000C/2h, 120C/12h

1470 MHz

• Largest improvement of

0 20 40 60 80 100 120 140

Bp (mT)

1E+090 20 40 60 80 100 120 140

Bp (mT)

T=2.0K Largest improvement of Q0 after 800 °C heat treatmentR d ti f h fi ld

1E+10

Q0

• Reduction of quench field above 800 °C (furnace contamination?)1E+09

0 20 40 60 80 100 120 140

Baseline (BCP) 1200C/2h, 120C/12h

)0 20 40 60 80 100 120 140

Bp (mT) Gigi Ciovati

Figure of merit of large & fine grain Niobium

Figure of merit is the product of (Eacc* Qo) at the quench limitCurrently magneto thermal quench limits the performanceCurrently magneto thermal quench limits the performance

Polycrystalline niobiumLarge grain ingot niobium

5.00E+11

6.00E+11

2.50E+11

3.00E+11

V/m

)

3.00E+11

4.00E+11

cc (M

V/m

)

1.50E+11

2.00E+11

t (Q

o.Ea

cc)

(MV

1.00E+11

2.00E+11Qo.

Eac

Prior to heat treatmentAfter heat treatment

5.00E+10

1.00E+11

Figu

re o

f Mer

it

0.00E+000 200 400 600 800 1000

Tantalum Content (Wt ppm)

0.00E+000 200 400 600 800 1000 1200 1400

Tanatlum Contenet (wt ppm)

SAITO/KEK

All available at DESY up to now Q(Eacc) of LG 9-cell cavities (AC112 was not baked) DESY

1,00E+11

AC112

1,00E+10Qo

AC112AC151AC155AC153AC154AC154AC157AC114AC113

XFEL

1,00E+090 5 10 15 20 25 30 35

Eacc. (MV/m

XFEL requirements Eacc =24 3 MV/m fulfilled in first testXFEL requirements Eacc 24,3 MV/m fulfilled in first test. Eacc 25 - 30 MV/m stably reachable after ca. 120µm BCP

TTF, 800°C+BCP LG, 800°C+BCP

DESY

253035

m

10152025

Eacc

, MV/

m

05

10

150 200 250 300 350 400 450 500 550

E

C i f th E f f l i (LG) 9 ll iti

150 200 250 300 350 400 450 500 550

RRR of Cavity measured by Eddy Current method

Comparison of the Eacc performance of large grain (LG) 9-cell cavities with similarly treated fine grain TTF cavities.

BCP k f LG b tt d t fi i itiBCP works for LG better compared to fine grain cavities

ConclusionsJL b i t d d i t i bi t h l i 2004• JLab introduced ingot niobium technology in 2004

• High tantalum in ingot niobium is not expected toHigh tantalum in ingot niobium is not expected to negatively impact the performance of the cavities but will reduce the cost of accelerator structures considerably

• A clean UHV furnace with induction heating will eliminate contamination of cavity surfaces and avoid the finalcontamination of cavity surfaces and avoid the final chemistry (Development with Casting Analysis Corporation)

• Optimized low cost CW linacs built with ingot niobium will pave the path for future R&D and industrial applicationspave the path for future R&D and industrial applications