3/20/2006

2006 KEKB Review

1Purpose• Check the assembly of the cryostat
although the coaxial beam pipe is not installed• Check whether the leak occurs or notduring cool-down and warm-up• Check the mechanical strength for the vibration
during moving it to the experimental site
• Measure the coupling @ 4.2K
• Measure the static loss of the cryostat
This time not using the high power from Klystron, but we did the low power test.

3/20/2006

2006 KEKB Review

2After the vertical test for the prototype crab cavity …
After HPR, the vertical test was succeeded.

After pulling up the cavity from the cryostat …

Contamination

HPR

A few screws at the indium flange loosened after the vertical test.
Then we re-tightened them.

3/20/2006

2006 KEKB Review

3The leak trouble occurred.
After setting the cryostat into the pit, we started the vacuum evacuation, but …
Unfortunately, the leak was found at the indium seal.
We must break up the helium jacket.
Then we must re-assemble the cryostat including re-welding the helium jacket etc.
Although we could not observe the exact leak point,
we presumed that the screws were not firmly tightened
and the indium seal was detached,because the holes for them were a little shallow totally.
And, we exchanged the screws for the shorter ones by 5mm.

In the end of January, the cryostat was moved to the pit again.

3/20/2006

2006 KEKB Review

4Carrying the cryostat into the pit @D10 (1)Setting the base

16t crane

Leveling the ground

Picking up the truck
Hoistingthe cryostat
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2006 KEKB Review

Moving to D10 site

5

Carrying the cryostat into the pit @D10 (2)A little dangerous situation
The center of gravity for the cryostat is high.

Moving slowly

Arriving at D10 site

Narrow space in the pit

Pulling down to the pit
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2006 KEKB Review

6
Finished !

Attaching the new jig for the fixation of the coaxial beam pipe
when moving the cryostat to the pit

Attaching the super-insulation in the pit

The vibration measure

W.G.
Almost hitting the input coupler
when pulling down to the pit

3/20/2006

2006 KEKB Review

7The measurement during the cold test
• Static loss
⇒ about 30W (calculated by Nakai-san)• The resonant frequency (later)• QL (later)• Check the cable length for the pick-up probe using TDR⇒ no problem• Check the cable attenuation using the signal generator⇒ no problem
The cryostat stayed at 4.2K for about 8 hours.

3/20/2006

2006 KEKB Review

8HITACHI Display at the Refrigerator Control System
HITACHI EX 5000 System

Temperature at each valve

HITACHI refrigerator group enabled the cryostat to cool down all day.
And, they recorded each measurement value per 1 hour during the cold test.
3/20/2006

2006 KEKB Review

9The Vacuum and the Temperature during the cold test
The cooling down rate was increased from 2.8K/hour to 3.5K/hour.

No leak !
Warm-up

Cool-down

10 days
The bad vacuum due to the outgas during warm-up
Outgas sources are H2, N2, CO, H2O and CO2 etc.

3/20/2006

2006 KEKB Review

10The displacement along the horizontal axis of the input coupler
The input coupler was pulled down to the cavity side, because the cavity shrank during cool-down.
The sudden change occurred during the cool-down, and it was the continuous change, not accidentally.

Cool-down~1.5mmWarm-up

Sudden change

The cool-down rate was changed from 2.8K/hour to 3.5K/hour
around this time.
And the cryostat vacuum also became bad.

Changing continuously !

3/20/2006

2006 KEKB Review

11The displacement of the input coupler along 3 axes
The input coupler was pulled down to the large beam pipe totally.

Coaxial beam pipe (free)

Cool-down
1.5mm

Warm-up

Input coupler
1.5mm

0.5mm

0.5mm

Large beam pipe (fixed)

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2006 KEKB Review

LBP was not moved due to the fixed end.

12

Temperature channel assign
The thermocouples were attached to the various sites.

Not installed

3/20/2006
H.Nakai

2006 KEKB Review

13

The temperature @ each thermocouple
Temperature on the thermal anchor

Inlet / outlet of N2 line

The thermal anchor worked well.

insidemiddle
outsideN2 line had no problem.

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2006 KEKB Review

14

Beginning to cool down from outside to inside

The measurement of the resonant frequency and QL using network analyzer

Network Analyzer

TDR

Input Coupler

Pickup Port

●The change of the resonant frequency due to the cavity shrinking●QL @ 4.2K
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The resonant frequency trend
The cavity was not pre-tuned, because it is not used for the operation.
The resonant frequency was changed by about 0.6MHz from the room temperature to 4.2K.

The measurement by S21 also became possible
below Tcavity=60K.
The both resonant frequencies were same below Tcavity=60K
for the measurement used by both S11 and S21.
~0.6MHz

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2006 KEKB Review

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The resonant frequency and QL below Tcavity~60K

506.77MHz
1.3x106
QL=1x106 (estimation)
8.6x105

After the cavity reached 4.2K, the resonant frequency and QL were changed considerably (8.6x105 → 1.3x106).
The inner conductor of the input coupler was cooled down ?
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2006 KEKB Review

17

The spectrum of the Network Analyzer @ 4.2K
12:14

15:11

8.6x105

1.0x106

18:36

1.3x106

Normally, such a phenomenon is not observed for the accelerating cavity.
From slowly changing, the temperature effect is supposed.
But, we don’t understand this phenomenon clearly !

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2006 KEKB Review

18Moving from D10 site to STF
Passing in front of TSUKUBA site

3/20/2006Setting
it below the helium gas bag

2006 KEKB Review completed19

Summary• The cold test was completed successfully without the leak.
• The resonant frequency was changed by about 0.6MHz
from the room temperature to 4.2K.
• QL=8.6x105~1.3x106 @ 4.2K (estimated 1.0x106)
We don’t understand the reason for the changing QL.

• Static loss was about 30W.
• The input coupler was drawn to the fixed end (LBP).
• The refrigerator system had no problem.

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