RF System for SuperKeKB＊
The 16th KEKB Accelerator Review Committee
2011.02.08

KAGEYAMA, T.
on behalf of
KEKB RF Group＊SuperKeKB stands for Nano Beam Scheme.

1Contentsn

RF system Overview✤

RF-related Machine Parameters✤

Upgrade Plansn

ARES CavitynSuperconducting Cavityn

New Digital LLRF System“Cavity for Damping Ring” reported by T. Abe right after my talk.

2

A big change brought after the previous review.

RF-­‐related	
  machine	  parameters
unit

SuperKEKB	
  (design	
  as	
  of	
  Feb.	
  2010)SuperKEKB	  (design	
  as	
  of	
  Nov.	
  2010)

Ring

LER

HER

LER

HER

HER

HER

Wiggler

Full

None

Full

None

60	
  %

Full

Beam	
  Energy

GeV

4.0

7.0

4.000

7.007

7.007

7.007

Beam	
  Current

A

3.60

2.62

3.6

2.6

2.6

2.6

2503

2503

2500

2500

2500

2500

Number	  of	
  Bunches
Bunch	
  Length

mm

6

5

6

5

5

5

Energy	  loss/turn

MV

2.15

2.50

1.87

2.07

2.43

2.67

	
  	
  	
  	
  	
  2.74E-­‐4

	
  	
  	
  	
  1.88E-­‐4

3.49E-­‐4

4.55E-­‐4

4.55E-­‐4

4.54E-­‐4

Momentum	  compacSon
RadiaSon	  Loss	
  

MW

7.74

6.55

6.73

5.38

6.32

6.94

Loss	
  factor,	
  assumed

V/pC

25

40

30

40

40

40

ParasiSc	
  Loss

MW

1.30

1.10

1.56

1.09

1.09

1.09

Total	
  Beam	  Power

MW

9.04

7.65

8.30

6.47

7.41

8.03

RF	
  Voltage

MV

8.4

6.7

9.4

12.4

14.7

15.8

HER RF Voltage almost doubled or more!
3

Consequently, the reversed-phase operation of SCC not being needed
although successfully demonstrated in KEKB.

Details reported by Y. Morita last year.
4RF-­‐related	
  machine	  parameters
unit

KEKB	
  (operaSon)K.	
  Akai	  (Nov.	
  25,	  2010)	
  SuperKEKB	  (design	
  as	
  of	
  Nov.	
  2010)

Ring

LER

HER

LER

HER

HER

HER

Wiggler

Full

None

Full

None

60	
  %

Full

Beam	
  Energy

GeV

3.5

8.0

4.000

7.007

7.007

7.007

Beam	
  Current

A

1.8

1.4

3.6

2.6

2.6

2.6

1585

1585

2500

2500

2500

2500

Number	  of	
  Bunches
Bunch	
  Length

mm

6	
  ~	
  7

6	
  ~	
  7

6

5

5

5

Energy	  loss/turn

MV

1.5

3.5

1.87

2.07

2.43

2.67

3.49E-­‐4

4.55E-­‐4

4.55E-­‐4

4.54E-­‐4

6.73

5.38

6.32

6.94

Momentum	  compacSon
RadiaSon	  Loss	
  

MW

2.7

4.9

Loss	
  factor,	
  assumed

V/pC

30

40

40

40

ParasiSc	
  Loss

MW

1.56

1.09

1.09

1.09

Total	
  Beam	  Power

MW

~	
  3.5

~	
  5.0

8.30

6.47

7.41

8.03

RF	
  Voltage

MV

8.0

15.0

9.4

12.4

14.7

15.8

5

e+

8 GeV x 1.4 A

3.5 GeV x 1.8 A

Vc = 15 MV,

Vc = 8 MV,

Pbeam = 5.0 MW

Pbeam = 3.5 MW

by

by

NIKKO

12xARES + 8xSCC

20xARES

D10

D5

OHO

D11

e-

D4

KEKB RF System

D5-C
D5-E

Klystron
SCC
ARES

D8

FUJI

D7
6

Two Types of Accelerating Cavities for KEKB
32 Normal Conducting (NC)
ARES Cavities:
20 for LER and 12 for HER

8 Superconducting (SC) Cavities
for HERe- beam(HER)

e- beam(HER)

e+ beam(LER)

Nikko RF Section D11

Fuji RF Section D7

7

RF Upgrade Plan (commissioning stage)

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8SuperKeKB will start up with
e-

e+

7 GeV

4 GeV

Vc = 15~16 MV

Vc = 9.4 MV

by

by
22xARES

D11

D4

8xARES + 8xSCC

OHO

NIKKO
D5

D10
Klystron
SCC
ARES

D8

FUJI

D7
9

RF Upgrade Plan (ultimate stage)

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  Akai	  (Nov.	
  25,	  2010)	
  

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10

e-

e+

7 GeV x 2.6 A

4 GeV x 3.6 A

Vc = 15~16 MV

Vc = 9.4 MV

Pbeam = 8.0 MW

Pbeam = 8.3 MW

by

by

D11

22xARES

D8

D7

OHO

NIKKO

8xARES + 8xSCC

D4SuperKeKB RF System at Ultimate Stage

D5

D10
Klystron
SCC
ARES

FUJI

2010.11.25
11One-to-Two Configuration of NC RF System (regular in KEKB)

SurfaceDive

2 x Pwall(~150kW) + 2 x Pbeam(~200kW) = ~700kW / Klystron

One klystron drives two ARES cavities.

12One-to-one configuration of NC RF system (major in SuperKeKB)

Surface

Dive

Pwall(~150kW) + Pbeam(~550kW) = ~700kW / Klystron
One klystron drives one ARES cavity to deliver more power to the beam.
Two RF stations D5-C & E had been operated with this conﬁgurationfrom Sep. 2005 through June 2010.

13

SC RF system for SuperKEKB(the same as for KEKB)
Dummy Loads�
Klystron�

Circulator�

Surface

Dive

SC Cavity�Vc = 1.5 MV, Pbeam = 400 kW

One klystron drives one SC cavity.

14

Toshiba CW Klystron E3732 (1 MW, 509 MHz)

Collector(evaporative cooling)
Output Coupler

Output Cavity
Waveguide Port
RF Window

Middle Cavities

Coaxial Line

Anode
CathodeInput Cavity

Electron Gun

Heater

As for the klystron, operation at around 800 kW is feasible, especially for the NC RF station.
• Klystrons, power supplies and high-power RF system can be operated stably.
• Existing components can be used without modifications.
• Sufficient margin to saturation of klystron.

15

Instability due to RF cavities and cure
Ring

Longitudinal/Transverse

Cause

Frequency (MHz)Growth time (ms)

Cure

LER

Longitudinal

ARES-HOM

1850

12

B-by-B FB

ARES-0/π

504

21

B-by-B FB-1 mode508.794-1 mode damper

LER

Transverse

ARES-HOM

633

7

B-by-B FBHERLongitudinal

ARES-HOM

1850

59(no need)

SCC-HOM

1018

58(no need)-1 mode508.794-1 mode damper

ARES-HOM

633

39(no need)

SCC-HOM

688

14

B-by-B FBHERTransverse

Longitudinal bunch-by-bunch FB will be needed
to suppress coupled bunch instabilities driven by RF cavities.

16

reported by K. Akai last year

Bunch gap transient• Phase	  modulaSon	
  along	  a	
  bunch	  train	
  caused	
  by	
  an	
  abort	
  gap
ω rf ⎛ R ⎞
Pb Δt
Δφ =
⎜ ⎟ × Ib Δt =2Vc ⎝ Q ⎠
2cos φ sU• KEKB– Owing	
  to	
  €high	
  stored	  energy	
  of	
  the	
  ARES	  and	
  SCC,	
  transient	
  phase	  modulaSon	
  (also	
  longitudinal	
  posiSon	
  change	
  of	
  beam)	
  is	
  small,	
  about	
  3	
  to	
  
5	
  degrees.	
  No	
  luminosity	
  degradaSon	
  along	  a	
  train	
  is	
  observed.
– CalculaSon	
  and	
  measurements	
  agree	
  well.	
  • SuperKEKB– Since	
  the	
  beam	  current	
  is	
  twice,	
  the	
  gap	
  length	
  should	
  be	
  reduced	
  to	
  about	
  half	
  (500ns	
  -­‐-­‐>	
  250ns)	
  to	
  keep	  the	
  same	  phase	  modulaSon.	
  Rise	  Sme	  of	
  the	
  abort	
  kicker	
  needs	
  to	
  be	
  improved.	
  	
  

17

K.	
  Akai	  (Nov.	
  25,	  2010)	
  18

Summary for RF System Upgrade• A new upgrading strategy is presented, responding to a big change in the beam optics design.
The RF voltage required for SuperKeKB HER has been almost doubled and settled aroundthe same level as for KEKB HER. Concerning the beam loading issues reported last year, thebalance between the beam power and the RF voltage has been normalized. Consequently,
the reversed-phase operation of SCC is not being needed.
– The beam powers required for HER (with wiggler magnets newly added) and LER increase 1.5 times and 2.5 times as high as
for KEKB, respectively. On the other hand, the total RF voltages for both rings remain almost the same level.
• Need to increase the beam power per cavity by two times or more, especially for ARES cavity.
• Need to increase the number of RF stations where one klystron feeds one ARES cavity with RF power up to 800 kW.
– At each RF station, operation at around 800 kW is feasible:• Klystrons, power supplies and high-power RF system can be operated stably.
• Existing components can be used without modifications.
• Sufficient margin to saturation of klystron.
– The beam power per ARES cavity to be increased from 200 kW (KEKB) to 550 kW or more (SuperKeKB).
• The input coupler for ARES cavity needs to be upgraded: The handling power 400 kW → 800 kW, and the input coupling
factor 3 → 6.
– OHO RF section D4 for HER:
• Increase the number of ARES cavities from 6 to 8, and every ARES cavity to be driven by one klystron at the ultimate
stage.
– OHO RF section D5 for LER:
• Convert 6 ARES Cavities from HER to LER, and every ARES cavity to be driven by one klystron from the commissioning
stage.
– FUJI RF sections D7 and D8 for LER:
• Remove 4 ARES cavities to optimize the ratio of beam power per RF voltage for LER.
– NIKKO RF sections D10 and D11 for HER:
• All of the 8 superconducting cavities remain the same as for KEKB.
• Every SCC to be operated with Vc = 1.5 MV and Pbeam = 400 kW.

19

ARES Cavity System
PHOM = 3.3 kW /HWG
✔ Tested up to 5 kW at test stand D1-C.

Input Coupler

HOM Waveguide (HWG) :Two SiC bullet-shaped
absorbers per HWG.

Storage Cavity(SC)
Input Coupling Factor
β = 6 (max.)

Parasitic (0 & π )Mode Damper

PHOM = 0.93 kW /Groove✔ Tested up to 1.2 kW at D1-C.

Coupling
Cavity (CC)

Grooved Beam Pipe (GBP):
Eight SiC Tiles per Groove.
Accelerating
Cavity (AC)ΔfAC = -280 kHz

PPMD = 21 kW
to 40-kW dummy load.
✔ Tested up to 24 kW at D5-C.

Pinput = 800 kW (max.)✔ Tested up to 800 kW at the test stand D1-A,
and up to 770 kW with beam at D5-C.
Pwall = 150 kW (Vc = 0.5 MV), Pbeam = 550 kW, PPMD= 21 kW
20Fundamentals of ARES Cavity System

Δfπ/2 = ΔfA / (1+US/UA )-28 kHz-280 kHz9

Flywheel Energy Ratio US/UA = 9 not changed.

21

e+

1.5 MV

7 GeV x 2.6 A

4 GeV x 3.6 A

P beam 400 kW

Vc = 15~16 MV

Vc = 9.4 MV

Pbeam = 8.0 MW

Pbeam = 8.3 MW

by

by

Vc

D11

8xARES + 8xSCC

22xARESNIKKOD10LER ARES

1 : 1

1 : 2

Vc

0.48 MV

0.34 MVP wall140 kW

70 kW

P beam

460 kW

230 kW

Input β

4.3

4.3

PPMD

14 kW

7 kW

0.5 MVP wall150 kW

P beam

600 kW

Input β

5.0

PPMD

21 kW

OHO

e-

Vc

D4

HER SCCHER ARES

D5SuperKeKB L = 8 x 1035 cm-2s-1

Klystron
SCC
ARES

D8

FUJI

D7

2010.11.25
22

Coupled Bunch Instability (CBI)
driven by the Accelerating Mode (π/2)Δfπ/2 = -28 kHz
KEKB LER
20 x ARES (0.4 MV, β＝3)Δfπ/2 = -17 kHz for 1.8 A

Re(Z//) / Cavity [Ω]SuperKeKB LER
22 x ARES (0.48MV, β = 5)Δfπ/2 = -28 kHz for 3.6 A
Δfπ/2 = ΔfAC / (1+US/UA )( f - frf ) / frev

23

CBI due to the Accelerating Mode (π/2)

10µ = -1µ = -2µ =- 3Rad. damping time

Growth Time [s]

1

0.1

0.01
SuperKeKB LER

0.001

22 x ARES (0.48 MV, β = 5)

τ (-1 mode) = 4 ms for 3.6 A
0.0001
0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Beam Current [A]24

(R+ − R−) / Cavity [Ω]Re(Z//) / Cavity [Ω]CBI due to the Impedance Imbalance
between the Parasitic 0 and π Modes

SuperKeKB LER 3.6 A(22 ARES Cavities)
τ = 21 ms for ΔfAC = -280 kHz

KEKB LER 1.8 A(20 ARES Cavities)
τ = 70 ms for ΔfAC = -170 kHz( f - frf ) / frev

25

22 ARES Cavities operated
for SuperKeKB LER ( I beam = 3.6 A )RF frequency

508.869 MHz

Flywheel Energy Ratio US /UA

9unchanged

Cavity Voltage Vc

0.48 MVP(wall) = 140 kW

Detuning Frequency Δfπ/2 / ΔfAC

-28 kHz / -280 kHz

P(beam) = 460 kW

Input Coupling Factor β

5.0

β (optimum) = 4.3

CBI (-1 mode) due to the Acc. modeτ = 4 ms

RF feedback

CBI due to the 0 and π modesτ = 21 ms

bunch-by-bunch FB

26

Input Coupler Upgrade
Monitor port
for arc detection
Door-knob transformer
from rectangular WG
to coaxial line

Over- and under-cut structure
for impedance matching
Ceramic RF window

Fine grooving on the outerconductor surface (yellow part)to suppress multipactoring
discharge. (by T. Abe)

Coaxial Line WX77D

Coupling
Loop

RF Power
400 kW for KEKB
800 kW for SuperKeKB

Monitor port
for arc detection

ICF-203
FlangeCoupling Loopextended
from 20 mm to 60 mm.

Capacitive iris27

Fine circumferential grooving on the outer conductor surface
in order to suppress multipactoring discharge.

T. AbeSuccessfully tested and used in actual KEKB operation.

28

Input Coupling Factor vs. Loop Height-3 %Unloaded Q Value

β (Input Coupling Factor)

copper spacers

Prototype

KEKB

Loop Height [mm]Loop Height
K. Yoshino, H. Sakai, T. Kageyama

A prototype coupler with a loop height of 60 mm
was fabricated in JFY 2009.

29

Temperature Distribution for the Coupling Loopextended to 60 mm.
〜87 °Cmm
60

Flow rate 3L/min. of cooling water (30°C)
for each of the inner and outer conductor.

K. Yoshino

30

Prototype Coupler was tested up to 800 kW.
(Apr. 12~23, 2010)
Storage cavity

Input coupler under test
Input coupler usedas output coupler

To 1MW water load

RF Power from
1MW CW Klystron(Toshiba E3786)

High Power Test Stand D1-A
31

Prototype Coupler attached to the ARES Cavity at D5-C.
(Apr. 27, 2010)

K. Yoshino, H. Sakai, T. Kageyama

32Input Coupling Factor set at β = 6.4 (cold).

K. Yoshino

33

Test Operation of the ARES Cavity at D5-C
with the Prototype Coupler for SuperKeKB.
(June 24, 2010)←HER Beam Current (mA)
←Cavity Input Power (kW)

Vacuum Pressure →(CCG reading in V)←Reflected Power (kW)10-7 Torr

10-8 Torr

Vacuum Pressure

RF Power [kW]HER Beam [mA]

10-6 Torr

10-9 Torr

Y. Yoshimoto, K. Marutsuka, T. Kageyama

34

ARES Cavity D5-C successfully delivered 610 kW to the beam.
Kly. Output =800kW / Cavity Input=770 kW
Vc= 0.47 MV
Pwall= 133 kW / PAC = 53 kW
Pbeam= 610 kW
Preflection = ~1 kW
PPMD= 24 kW (meas.) / 24 kW (predicted)←Cavity Input Power (kW)

Vacuum Pressure

RF Power [kW]10-6 Torr

10-7 Torr

Vacuum Pressure (CCG reading in V) →←Reflected Power (kW)HER Beam Current [mA]

10-8 Torr

10-9 Torr

Y. Yoshimoto, K. Marutsuka, T. Kageyama

35

HOM Loads for the ARES Cavity
PHOM = 3.3 kW /HWG
✔ Tested up to 5 kW at test stand D1-C.

HOM Waveguide (HWG) :Two SiC bullet-shaped
absorbers per HWG.
PHOM = 0.93 kW /Groove✔ Tested up to 1.2 kW at D1-C.
Grooved Beam Pipe (GBP):
Eight SiC Tiles per Groove.

36

HWG Load

400 mmああY. Takeuchi

Each HOM WG (HWG) is terminated with two bullet-shaped SiC absorbers.
The power handling capability = 2.5 kW / bullet (5 kW/HWG, or 20 kW/cavity).

37

GBP Load

300 mmY. Takeuchi

Each groove has eight SiC tiles in line, where every tile is brazed to a water-cooled copper plate.

38

High Power Test of GBP Load @D7-yoko (annex) in 2008

GBP Load

RF Window (PBX type)

RF Power fromL-band Klystron(1.3 GHz, CW)

Vacuum Pressure [Torr]

measured on Apr. 4, 2008

Waveguide (WR650)

RF Power [W]As reported last year, abnormal vacuum
pressure rise observed above ~1.2 kW.
Y. Takeuchi

39

High Power Testing of GBP Load
more precisely reflecting the actual environment.

Detach GBP from AC.

40

Setup for High Power Test of GBP Load
more precisely reflecting the actual environment.

RF Power
L-band WG(WR650)

GBP LoadRe

from
L-band Klystron(1.25 GHz, CW)

de
i
gu
e
v
a
W
P
B
G
er
o
m
-t for
r
s
la
n
u
g
ra
n
T
a
ct

Y. Takeuchi

41

High Power Testing of GBP Load @ D1C (from Oct. 2010 through Feb. 2011)
MO-Flange Connection

under construction

GBP Load under High-Power Test
Y. Takeuchi

42Results of High Power Test of GBP Load @ D1C (from Oct. 2010 through Feb. 2011)
Load inside GBP (measured on Feb. 2, 2011)
Load inside GBP (measured on Oct. 22, 2010)
Load inside WG (measured on Apr. 4, 2008)

20-hour operation at 1.2 kW
before going over 1.5 kW.

Y. Takeuchi

43Results of High Power Test of GBP Load @ D1C (from Oct. 2010 through Feb. 2011)

Feb. 4, 2011

No damage observed to the loads inside GBP
after 20-hour operation with 1.2 kW of RF power per groove.
Y. Takeuchi

44

HOM Power Estimation for SuperKeKB LERKEKB LER
Sep. 21, 2004

SuperKeKBLERPower Handling Capability
verified at 1.25 GHz

Factor of Safety

Ibeam [A]

1.6

3.6

-

-

Nbunch

1293

2503

-

-

σz [mm]

7

6

-

-

k [V/pC]

0.40 (0.39†)

0.44

-

-

PHOM /ARES
[kW]

5.4†

17

-

-

PHOM /HWG
[kW]

1.05†

3.3

5.0

5.0/3.3 = 1.5

PHOM /Groove
[kW]

0.3†

0.93

1.2

1.2/0.93 = 1.3†based on calorimetric measurement

45Summary for ARES Cavity System★ The ARES cavities can be operated for SuperKeKB LER (3.6 A) without increasing the ﬂywheel energy ratio (US/UA = 9).
Needless to say for SuperKeKB HER (2.6 A).
✔ The amount of frequency detuning for beam loading compensation: ΔfAC = -280kHz, that is |Δfπ/2| = 28kHz < frev = 99 kHz.
✔ CBI (τ= 4ms for the fastest -1 mode) drivne by the accelerating mode: Cured by RF feedback.
✔ CBI (τ= 21ms, out of the klystronʼs bandwidth limit) due to the impedance imbalance between the 0 and π modes:
Cured by longitudinal bunch-by-bunch FB.
★ Input Coupler✔ A prototype coupler was fablicated in JFY 2009, with ﬁne grooving on the outer conductor surface of the coaxial line
to suppress multipactoring discharge, and with the coupling loop extended from 17 mm to 60 mm to obtain the input coupling
factor over 6.

✔ The prototype coupler was successfully conditioned up to 800 kW at the test stand (Apr. 12~23, 2010).
✔ The prototype coupler was attached to the ARES cavity at D5-C (one-to-one conﬁguration), and successfully delivered 610 kW
to the beam (1250 mA) on June 24, 2010 (only 6 days before KEKB shutdown).
Fabrication of two pre-production couplers under way (JFY2010). Production of 6 couplers scheduled for JFY2011,
followed by 8 couplers for JFY2012 and 6 couplers for JFY2013.
★ HOM loads✔ The HOM waveguide loads: The power handling capability per WG veriﬁed up to 5 kW at a test stand with an L-band klystron.
There will be a 50% margin left with respect to the design limit of 3.3 kW per WG for LER (3.6 A).
✔ The GBP loads: The power handling capability per groove veriﬁed up to 1.2 kW at the test stand.
There will be a 30% margine left with respect to the design limit for LER (3.6 A).

46

Y. Morita

Superconducting Cavity System
Pinput = 400 kW
Tested up to 750 kW.

Input Coupling Factor(Qext~50000) not changed

PHOM = 19 kW
Tested up to 19 kW.

Needs to be renewedsince some major parts
not available.

PHOM = 26 kW
Tested up to 26 kW.

Vc = 1.5 MV, Pbeam = 400 kW

47

Superconducting cavities for SuperKEKB
Requirements and issues•

Superconducting cavity– Operating voltage: 1.5MV• Already achieved– Operating current: 2.6A (SpuerKEKB HER)
• Maximum current achieved: 1.4A (KEKB HER)•High power input coupler– Beam power: 400kW• Already achieved– Optimum coupling: Qext~50000• Present coupling (no need to change)•

HOM damper– Expected HOM power:45kW @ 2.6A
• Including self damper loss
• SBP damper:19 kW• LBP damper: 26 kW– Ferrite temperature becomes high in the present HOM damper• Need to suppress temperature rise– to suppress outgas which trigger cavity trips– R&D for new dampers to suppress temperature rise underway• Ferrite thickness: 4 →3 mm• Double cooling structure•

Tuner driver system– Need renewal of the piezo stack because of discontinuation of product•New electro-polishing facility– Renewal of the facility•

R&D for high pressure water rinsing– For cavity performance recovery– Rinsing of the cavity in the cryomodule

Y. Morita

48

Input couplers for SCC

Y. Morita

Air cooling

Beam power: 400kW (already achived)

WG

Door knob transition

Optimum coupling: Qext ~50000 (not changed)
Powerful cooling needed for 450kW operation

Cooling water

New coupler under test

Old type coupler

Door knob transition

Cooling water channel
D10 coupler Test standCeramic RF window

Conditioned up to 750 kW

No hard multipacting levelfrom 150 to 500 kW

Inner conductor atdoor knob
New type coupler
Simplified single cooling water path49

Y. Morita

Expected HOM power for SuperKEKB-HER•

Expected HOM power

Parameters of SuperKEKB HER
Maximum current: 2.6A
Bunch length: 5 mm
# of bunches: 2500
Loss factor: 1.2 V/pC

– at 2 A, 19 kW+ damper loss (8 kW)– at 2.6 A, 32 kW+ damper loss (13 kW)
Beam current

SBP load

LBP load

(A)

(kW)

(kW)

2

12

15

2.6

19

26

(KEKB-HER)(1.4 A)(6-7 mm)(1600)

Loss factor of the cavity structure

Beam pipe: 150Φ

LBP

SBP

Ferrite HOM damper

50

New HOM damper
Prototype #1
Improvements for higher power capacity
Surface temperature of the ferrite has to be decreased to suppress
outgas. Copper base pipe temperature also has to be decreased to
avoid ferrite cracking.
1) Thickness of ferrite was reduced from 4 mm to 3 mm.
2) The number of cooling channels was doubled.
High power test standHigh power test results(New LBP damper)

SBP damper also HP tested

Flow rates of the cooling water were 6, 8, 10L/min
Copper base pipe temperatures were blow 60℃

Input RF power vs absorbed power
LBP damper absorbed RF powers up to 24 kW

up to 18ｋW
Tｆ<150℃ and TCu<60℃

Absorbed power vs ferrite temperature
Temperature was 160℃ at 24kW

Y. Morita
51

Temperature distributionof copper base pipe
Double cooling structure can decrease
temperature rise of the copper base pipe.

Y. Morita

Temperature distribution at 14 kW

Prototype #1
RF power flow

Thermo-couple number

cc1
cc2

cc3

cc5
cc4

cc6

Several thermo-couples were attached on thecopper base pipe and temperature distribution
was measured.

A-type coolingSingle cooling structure

B-type cooling

Double cooling structure52

Y. Morita

2nd prototype dampers cracked during high power test•

Dampers cracked– LBP: 25kW absorption– SBP: 15 kW absorption•

Ferrite thickness is not enough ?

Microscopic picture of the crack53

Y. Morita

High power test results for HOM dampers
Damper type

LBP

SBP

Ferritethickness(mm)

CoolingchannelMax.
absorbed
power
(kW)

Ferritetemperature(℃)

KEKB type

4

Single26

170

Prototype #1

3

Double24

160

Prototype #2

3

Double26

170

KEKB type

4

Single19

190

Prototype #1

3

Double18

150

Prototype #2

3

Double

19

170

Crack

○

○

New LBP and SBP dampers with the ferrite thickness of 3 mm can absorb HOM power
expected for SuperKEKB HER (2.6 A).
However, the surface temperature of the ferrite was not reduced significantly as expected.
If this result is true, there is no merit to replace the present 4-mm-thick ferrite dampers
with new 3-mm-thick ferrite ones. In advance of the final decision, more investigation isneeded.
Furthermore, as for each of the 2nd prototype dampers for LBP and SBP, the ferrite layer
was cracked during the high power test. The tensile strength of 3 mm-thick ferrite may not
be enough.

54

A. Kabe

Tuner driver renewal•

Fabricated for TRISTAN SCC•

Consists of– Motor jack• Gear box• Jack bolt
• Slide base
• Limit SW• Potentiometer– Pulse motor (renewal)– Piezo-stack (renewal)

e
s
o
Th

u
o
h
s

e
b
ld

w
e
n
re

!
d
e

• Piezomechanik– Load cell
– Pulse motor driver (renewal)– PS for piezo-stack (renewal or revised)– Tuner controller•

Prototype fabrication and tests– A prototype tuner driver was fabricated– Tested at the test bench– Mounted on D10B cavity on 4/13, 2010
– Operated until shutdown on 6/30, 2010

Tuner driver– Successfully operated at the KEKB machine time55

S. Mitsunobu

New electro-polishing system for KEKB-SCC
Old EP system at Nomura Plating Co.
Horizontal and rotating system for electro-polishing developed for
TRISTAN superconducting cavities.

Rotating equipment and EP bed weretransferred to new EP facility at KEK.

New features
Automatic controlling system
Tight sealing for HF acidControl panel

56

S. Mitsunobu

New EP facility for KEKB-SCC
New EP equipment for SCC on 2nd Floor

Acid gas cleaning system

New 500 L reservoir for HF/H2SO4 solution

Ultra-sonic bath and shower tank57

S. Mitsunobu

Electro-polishing

1st EP for a test cavity
•
•
•
•
•

Removing solution

EP bed is moving to hold the cavity vertically.

Electrolyte solution: HF(45%):H2SO4(96%)=1:9
Acid temperature: 20~30 ℃
Cathode voltage: -20~-30 V
Current density: 30~50 mA (EPI>EPII)
Acid flow rate: 40L/min

Removing solution

Electrolyte solution is extracted while the cavity was vertically held.

58

S. Mitsunobu

4 bar shower rinsing with pure waterO3 rinsing

Ultra-sonic rinsing in a hot water bath59

Vertical test
Eacc＝13MV/ｍ was achieved after EP（＠KEK)
Test cavity was successfully electro-polished with new EP system

After EP
Before EP

60

S. Takano

Horizontal High Pressure Rinsing (in situ)
Degraded cavity might recover its performance with the high pressure ultra-purewater rinsing. In order to apply for cavities in operation, the rinsing has to be done
horizontally as shown in a figure below. An aspirator removes wasted water in acavity sell.

Nozzle head and stainless steel pipeNozzle head made of stainless steel (SUS410)

Rinsing a prototype cavity in a clean room

Ultra-pure water pressure : 60 bar
Holes : 6 holes, f0.54mm
Driving speed :	
10mm /15sec for LBP & SBP
	
5mm /15sec for Cell
Rotation speed : 60deg. / 5sec
Total time : 20 min.
Nozzle was manipulated manually.

61

Y. Morita

Summary for the Superconducting Cavity System
•

B
K
E
K
uper

Cavity– 1.5MV (achieved)– 2.6A (target)•

Input coupler– 400kW (achieved)– Need R&D for higher beam powers

•

W)
k
0
0
(4
s
r
e
S
W)
w
k
r
o
0
o
p
4
f
m
(>
s
ion
t
a
s
a
C
e
r
r
b
e
e
C
S
ow
op
igh
p
h
m
r
r
M
o
e
f
t
O
Need t coupler for high H s for longuer1) Inp M dampe rastructurf2) HO ewal of in
n
e
R
)
3

HOM damper– Two new damper sets fabricated and tested• Expected HOM powers @ 2.6A can be absorbed• Temperature rise not significantly reduced• 2nd prototype dampers cracked during high power test
– Need to study to understand above reasons•

Tuner driver– Renewal•

Infrastructure– Electro-polishing facility• Construction completed• To be used for cavities for the Taiwan Photon Source project– HHPR apparatus• Continue R&D

62

Y. Morita
p.18
23) Superconducting Cavity
The feasibility of “reversed-phase operation” of the superconducting HER cavities is critical to the RF system plan for Super KEKB.
Only by using this technique can the new RF demands be supported by existing hardware without major changes. By analysis andcareful test, the KEKB RF group have examined the issues and determined that none of them will prevent implementation of thisconcept; synchrotron tune, beam loading response,controllability, bunch length and transient trip response are all either
unchanged, or if changed are acceptable and controllable. Tests included support of a luminosity run at 1200 mA delivering 300
kW/cavity to the beam. The only unusual event was a rise in cavity voltage on a reversed-phase cavity during a beam energychange. A thorough investigation demonstrated that this was to be expected, and that the range of possible excursions at thenominal operating point is well within the tolerable operating range of the superconducting cavities.
HOM dampers will have to be improved to deal with beam currents in excess of 2 A, but this should be achievable withstraightforward extensions of the existing design. Design concept tests were successful and prototypes are being constructed forfurther proof.
Although the existing input couplers will meet the RF power requirements of SuperKEKB, further development of couplers forhigher power is ongoing.

-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐
Reply from Y. Morita to the above comments in the report from the 15th KEKB Accelerator Review Committee:
Reverse Phase Operation
We have no need for the reverse phase operation because the operating voltage of the superconducting cavity was set sufficiently
high enough to maintain normal phase operation in the new machine parameters.
HOM damper
The superconducting accelerating cavity has two dampers. One is a large beam pipe damper (LBP damper) with a beam pipe
diameter of 300 mm, and the other is a small beam pipe damper (SBP damper) with a beam pipe diameter of 220 mm. Thosedampers are required to absorb 25 kW in LBP and 18 kW in SBP, respectively, at the designed current of 2.6A.Surface
temperatures of the ferrite with those power absorption becomes high and outgas may cause cavity trips. In order to reducesurface temperature, we made two modifications. The first modification is to reduce thickness of the ferrite from 4 to 3 mm forbetter thermal conduction. The second one is make double cooling structure for better cooling to reduce temperature rise of thecopper base. We have fabricated two prototype dampers with 3mm thick ferrite and double cooling structure. Those dampers werehigh power tested and absorbed expected HOM powers of SuperKEKB. However, surface temperature of theferrite was not decreased as we expected. Those test results showed that the thickness reduction of the ferrite has little merit for
temperature decrease of the ferrite surface. Furthermore 2nd prototype dampers cracked during the high power test. The
thickness reduction may make the tensile strength of the ferrite insufficient. We have to re-examine the HOM damper for
SuperKEKB. We also have to examine to reduce the loss factor by using beam pipes with larger diameters.
High Power Input Coupler
We continue R&D for higher power handling.

63

K. Akai

New digital LLRF for SuperKEKB• System	  – Replace	
  old	
  analog	
  circuits	
  with	  digital	
  control	  – Replace	
  CAMAC	
  with	
  PLC– Measures	
  for	
  heavy	
  beam-­‐loading– CompaDbility	
  between	
  the	
  old	
  and	  new	
  systems	  (Commissioning	
  will	  start	  with	  both	  systems	
  exisDng.)• Digital	
  control	
  board– Digital	
  LLRF	
  board	  is	
  being	
  developed,	
  common	
  to	
  SuperKEKB	
  and	
  cERL	
  projects.	
  The	
  board	
  is	
  also	  planned	
  
to	
  be	
  used	  for	  collision	
  feedback	
  system.	
  – EPICS	  IOC	  on	  FPGA	  and	  EPICS	  IOC	  on	  PLC	  is	
  adopted,	  under	  collaboraDon	
  with	  KEKB	  control	
  group.

• Prototype– Will	  be	
  installed	
  at	
  D8-­‐D	
  staDon	  next	  month,	
  and	
  tested	
  with	
  klystron	
  and	
  ARES	  cavity	
  this	  year.

• ConstrucDon– Install	
  new	
  LLRF	  for	  new	
  staDons	
  where	  one	
  klystron	  drives	  one	
  ARES	  cavity.
– The	
  old	
  system	
  will	  be	
  kept	  for	
  staDons	
  where	  one	  klystron	
  drives	  two	
  ARES	  caviDes.	
  They	  may	  be	
  replaced	
  with	
  new	
  LLRF	
  in	
  future,	  depending	
  on	
  budget.	
  Block	  diagram	  of	
  new	
  LLRF	  for	  SuperKEKB

64

K. Akai

Block	  diagram	
  of	
  digital	
  LLRFμTCA	
  shelf

Digital	
  LLRF	
  board65

K. AkaiNew	
  LLRF	  for	
  one	
  staDon66

K. Akai
p.	
  3
7)	
  The	  conSnued	
  use	  of	
  the	
  older	
  analog	
  RF	
  low	
  level	  controls	
  on	
  the	
  exisSng	
  staSons	
  should	
  be	
  evaluated	
  for	
  compaSbility	  with	
  the	  new	  digital	
  systems,	
  which	  are	
  currently	
  only	  proposed	
  for	  the	  new	
  staSons.
p.	
  17
While	
  this	  plan	  meets	
  operaSonal	
  requirements,	
  reliable	
  implementaSon	
  will	  require	
  the	
  deployment	
  of	
  the	
  advanced	
  digital	
  Low	
  Level	  RF	
  control	
  circuitry	
  being	
  developed	
  by	
  KEK	
  and	
  its	  industrial	
  partners,	
  in	
  parallel	
  with	  most	  other	  accelerator	
  laboratories	
  around	  the	
  world.	
  Hardware	
  design	
  is	
  nearly	
  done	  and	  the	
  ﬁrst	  system	
  will	  be	
  installed	
  and	
  tested	
  later	
  this	  year.	
  The	
  only	  proposal	
  that	  is	  of	
  some	  concern	
  to	
  the	
  commiaee	
  is	
  the	
  suggesSon	
  that	  some	  of	
  the	  RF	  systems	
  would	  conSnue	
  to	
  be	
  operated	
  with	  the	
  old	
  analog	
  LLRF	  control.	
  The	
  reliability	
  and	
  simplicity	
  of	
  operaSon	
  achieved	
  by	
  a	
  
having	
  a	
  common	
  system	
  seem	  worth	  the	
  addiSonal	
  10	
  Oku-­‐yen.
-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐-­‐
Reply	
  from	
  K.	
  Akai	  to	
  the	
  above	  comments	
  in	
  the	
  report	
  from	  the	
  15th	  KEKB	  Accelerator	
  Review	
  Commiaee:	  (CompaSbility)The	
  present	
  LLRF	  system	  has	  been	  operated	
  successfully	
  up	
  to	
  2.0A	  in	
  KEKB.	
  Since	
  the	
  longitudinal	
  parameters	
  such	
  as	
  RF	
  
voltage,	
  bunch	  length	
  and	
  phase	
  stability	
  are	  not	  very	  much	  diﬀerent	
  between	
  KEKB	
  and	  SuperKEKB,	
  the	  present	
  system	
  could	  be	
  used	  without	
  problems,	
  at	
  least	
  up	
  to	
  about	  the	
  same	  beam	  current.	
  For	  the	
  one-­‐to-­‐one	
  staSons	
  (one	  klystron	  drives	  one	
  ARES	  cavity),	
  where	
  beam-­‐loading	
  becomes	
  heavier,	
  new	  digital	
  LLRF	
  will	  be	
  used.	
  The	
  old	
  system	
  will	  be	
  kept	  at	
  one-­‐to-­‐two	
  staSons	
  where	
  the	
  beam-­‐loading	
  is	
  lower.	
  In	
  addiSon,	
  compaSbility	
  on	
  signal	
  connecSons	
  between	
  the	
  LLRF	  and	
  outer	
  system	
  and	
  relevant	
  EPICS	  records	
  will	  be	
  kept	  as	
  much	  as	
  possible	
  between	
  the	
  old	
  and	  new	
  LLRF	  systems.	
  (AddiSonal	
  budget?)Considering	
  the	
  budget	
  and	
  schedule	
  for	
  whole	
  SuperKEKB	
  construcSon,	
  replacement	
  of	
  all	
  old	
  LLRF	
  staSons	
  with	  new	  digital	  ones	  by	
  T=0	
  does	  not	
  seem	  to	
  have	  higher	
  priority	
  than	  fabricaSng	
  and	
  installing	
  those	  components	
  that	  are	  absolutely	
  necessary	
  at	
  T=0.	
  Our	
  plan	  is	  to	
  install	
  new	
  LLRF	
  to	
  new	
  one-­‐to-­‐one	
  staSons	
  where	  no	
  LLRF	
  is	
  exisSng,	
  and	
  to	
  
keep	
  the	  present	
  old	
  systems	
  for	
  one-­‐to-­‐two	
  staSons	
  unSl	  when	  addiSonal	
  budget	
  would	
  allow	
  us	
  to	
  implement	
  new	
  systems	
  to	
  replace	
  old	
  ones.	
  	
  

67

In my personal view,the new digital and the old analog LLRF systems
will function in harmony as below.

By ANNE EISENBERG
Published: April 15, 2007

IPODS are fine for listening to music on the go, but sometimes
people want to cast headsets aside and hear their playlists piped
through the living room by a sound system.

http://www.nytimes.com/2007/04/15/business/yourmoney/15novel.html

Kageyama, T.
68

THANK YOU SO MUCH
FOR
YOUR ATTENTION.

69

FOLLOWED BY BACKUP SLIDES

70

M.	
  YoshidaD4	
  のKlystron	
  を3本→8本に増設するための電源棟内配置変更

D4棟

D4棟

現状図

最終8本増設案

検討事項
1) 循環型冷却水装置（1MW	
  DL用）の振動はSRモニタに影響はないか？
2) 凝縮水タンクの振動はSRモニタに影響はないか？
3) 蒸気装置は中央設置ではないが問題（圧力、給水能力）ないか？
71

D5	
  のKlystron	
  を4本→6本に増設するための電源棟内配置変更

M.	
  Yoshida72

D7	
  のKlystron	
  を5本→6本に増設するための電源棟内配置変更

M.	
  Yoshida73

D8	
  のKlystron	
  を5本→6本に増設するための電源棟内配置変更

M.	
  Yoshida

74

75

76

77

78

Tuning Range for the Resonance Frequencyof the Accelerating Cavity when fRF = 508.869 MHz-140 kHz+100 kHz508.869 MHz-390 kHz

Accelerating Cavity Freq. [MHz]from Freq. Meas. Data for AC#03~#25
out of ARES Cavity Production AC#01~#28 at MHI

fRF
fH
fave
fL
-5 mm

+50mm

Tuning Plunger Insertion [mm]Min | Δf tuner + Δf thermal | = 370 kHz > |ΔfAC | = 280 kHz
Δf tuner = -290 kHz ~ -530 kHz
Δf thermal = -80 kHz for ΔT = +10 K
not include Δf (tuner travel from 0 mm to -5 mm) = ~ -100 kHz
79

R&D being continued.

ARES-KAI(originally designed for SuperKEKB)

アレス改

T. Abe and Y. Takeuchi

Replace the grooved beam pipes with winged chambers.
Each wing equipped with a bullet-shaped SiC absorber.
80

Winged Chamber loaded with two bullet-shaped SiC Absorbers
under High Power Test @ D1C. (Aug. 2010)

Y. Takeuchi and T. Abe

Successfully tested up to 10 kW per chamber / 5 kW per wing.

81

Setup for High Power Test of Winged Chamber

Y. Takeuchi and T. Abe

3D Schematic View

82

Vc=1.56MV

Reverse phase operation
Merit of reverse phase operation
１）Low total voltage while each cavity voltage is highNo need to change coupling constant
Small detuning
２）Reverse phase cavity also gives beam power
Beam study
Low current study （150ｍA）
Measured bunch length, synchrotron tune, beam loading when
the beam phase of single cavity was reversed.
High current study （１A)
Measured voltage variation of the reversed cavity when thenormal phase cavity trips.

Phasor presentation of cavity voltage

Reverse phase‐ΦsNormal phaseΦs0.3MV increased at the trip (acceptable)
83

A. Kabe

New tuner driver

D10B cavity in the tunnel

Removing old tuner driver

Removing old tuner driver84

A. KabeMounting new tuner driver

Mounting new tuner driver

Mounting completed

Support arm attached85

A. KabeConnecting cables

Cables connected

Tuner driver exchange completed86

TERMINATOR

87