overview of the 8 mcp resistances measured at aps/hep · 6/20/2013 · overview of the 8" mcp...

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Overview of the 8" MCP resistances measured at APS/HEP(February 2012 - June 2013)

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Scope channelAnode

Photo-cathode UV laser light

2mm grid spacer

4.45mm grid spacer

Top MCP

Bottom MCP

Vent slots

Typical Vertical Slice

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Stack compression: 4x50lb compression screws

plusatmospheric pressure

(when pumped)

Demountable(typical vacuum gauge reading

~ 1e-6 torr)

Stack compression: cross bars screwed onto the tray

8“ chamber(typical vacuum gauge reading

~ 1e-8 torr)

Test Setups

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groundGlass or ceramic insulationbetween ground and

HV copper electrode

Stack compression: Flexible aluminum top plate

(internals are compressed with atmospheric pressure when pumped

IR-ISS (for imaging with IR camera)

Copper electrode sits on a ceramic insulator at the bottom of the ISS.Grid spacer or MCP is compressedwith quartz window. Ground connectionis provided by the top electrode.

Test SetupsSpacer Station (ISS): „resistance measurements station“

(typical vacuum gauge reading ~ 1torr - 1e-5 torr)

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Observation IChem-2 plates in the 8" chamber

Plate # Passivation Resistive layer

SEE layer

Annealing Resistance(measured when received), MOhm

12258-543

3nm Chem-2, 68nm

Al2O3, 6nm 4hrs@400C ~20

12258-540

3nm Chem-2, 68nm

Al2O3, 6nm 4hrs@400C ~40

I.A) Non-linear I-V curve of 20MOhm plate (top of the stack) after 3 days of testing

Feb-Apr 2012

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Observation IChem-2 plates in the 8" chamber


SEE layer


12258-543

3nm Chem-2, 68nm

Al2O3, 6nm 4hrs@400C ~20

12258-540

3nm Chem-2, 68nm

Al2O3, 6nm 4hrs@400C ~40

I.B) Plate 12258-543 went back to linear I-V after ~1week, but resistance dropped to 3MOhm and remained such till the end of testing (April 2012).

I.C) Plate 12258-540 gradually dropped to 3MOhm after ~3 month of testing

I.D) Decreased resistance didn't restore even when plates were not at HV for a week

I.E) Vaccum has never been broken during 3 months of testing

„Testing“ implies that plates were held at ~1kV during the day time several days a week when timing characteristics were tested with the fast laser.

Feb-Apr 2012

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Observation IIChem-2 plates in the demountable


SEE layer


12258-544

3nm Chem-2, 75nm

Al2O3, 20nm 4hrs@400C ~10

12258-536A

3nm Chem-2, 70nm

Al2O3, 5nm 4hrs@400C ~10

II.A) These plates were extensively used in various configurations of the demountable (single anode tile, 4-anodes row, etc.). Stable operation, no special attention paid to the resistances.

Full stack resistance: R(MCPs)~20MOhm + R(grids)~10MOhm

=~ 30 MOhm

May-Oct 2012

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Observation IIChem-2 plates in the demountable


SEE layer


12258-544

3nm Chem-2, 75nm

Al2O3, 20nm 4hrs@400C ~10

12258-536A

3nm Chem-2, 70nm

Al2O3, 5nm 4hrs@400C ~10

II.B) Full stack resistance decreased by 25%after dedicated life test. During this test the demountable was held at 2700V for 1 week.

II.C) Decreased resistance didn't restoreafter voltage was off for a few days.

II.D) After life test all components were placed intoISS individually. (vacuum inside the ISS was ~1e-1 torr).- Grid spacers: no resistance change.- MCPs: 25% and 40% resistance drop for top and bottom

Electric current going through the full stack as a function of time at constant voltage of 2.7kV

Jan-Feb 2013

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Observation IIIChem-1 plates in the demountable


SEE layer


13600-002

0nm Chem-2, 52nm

Al2O3, 12nm 4hrs@400C ?15 (pre-anneal) → 25

(post anneal)13600-003

0nm Chem-2, 5nm

Al2O3, 12nm 4hrs@400C ?14(pre-anneal) → 22

(post-anneal)

We did not measure the resistance of these plates individually prior demountable assembly, we only assumed their resistances to be very close.

III.A) Initial resistance of the full stack 54 Mohm. After subtracting 8MOhm contribution of the grids and assuming equal resistance of the plates, the individual resistance of the MCPs is 23 MOhm (consistent with post-anneal measurements)

III.B) After 2 hrs at 2.7kV full stack resistance was 45 MOhmIII.C) After 1 day at 2.7 kV full stack resistance was 35 MOhmIII.D) After 2 days at 0 voltage the resistance remained 35 Mohm

III.E) Vent to air due to pump failure (time in air 2-3 weeks). Pumped again and measured the resistance of the full stack of 50 Mohm. (06/20/2013)

Apr 2013

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Observation IVChem-2 plates in the IR-ISS

IV.A) R=50MOhm for the stack consiting of a plate #12258-540 placed in IR-ISS on top of 10MOhm 4.45mm grid spacer

IV.B) R=10MOhm for the stack consisting of just one MCP #12258-540 placed at the bottom of the ISS with no grid spacer and covered with copper electrode

● Same plates that were used in 8“ chamber tests (12258-543 and 12258-540)● The assumption was that these plates are still 3MOhm and if it's local we would see bright spots with IR camera through quartz window in the ISS.

MCP

Grid Spacer

MCP

1.1kV

1.1kV

June 2013

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IV.C) R=41MOhm for the stack consisting of MCP #12258-540 placed at the bottom of the ISS with 10MOhm 4.45mm grid spacer and covered with copper electrode, but the bottom of the MCP is shorted to the ground

IV.D) R=34MOhm for the stack consisting of MCP #12258-543 placed at the bottom of the ISS with 10MOhm 4.45mm grid spacer and covered with copper electrode

MCP

Grid Spacer

MCPGrid Spacer

1.1kV

1.1kV

June 2013

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MCPGrid Spacer

32

33

34

35

36

37

38

0 20 40 60 80

Series1

29

30

31

32

33

34

35

0 20 40 60 80

Series1

IV.E) Stack resistance for the configuration IV.D changes over time when kept at 1100V.

1.1kV

Cur

rent

, muA

Time, hours

Res

ista

nce,

MO

hm

Time, hours

MCP+GS MCP+GS

June 2013

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MCPGrid Spacer

0

5

10

15

20

25

30

0 20 40 60 80

Series1

Res

ista

nce,

MO

hm

Time, hours

MCP onlySubtracting 10MOhm

contribution from Grid Spacer

June 2013

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Observation VChem-2 plates in the IR-ISS

Fingerprints to determine the boundaries of the MCP

June 2013

2.3kV

This test is in progress as of 06/21/2013

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Thoughts and Ideas● Resistance change may not be permanent and can be restored by venting to air● Air traps can contribute (in parallel) a few MOhms to the total plate resistance● Two types of traps

- mechanical contact with the grid spacers

- substrate quality (random pores are blocked? cleaning? production?)● SEE layer around these air traps may be responsible for the resistance change

when plate is kept under HV● More data needed to make sure that the resistances go back to their inital values

after some time in air.

If true:

● MCPs with low nominal resistance (<MOhm) should be stable in life tests (given we can avoid thermal runaways in the resistive layer)

● MCPs with no SEE layer should behave differently in life tests

overview of the 8 mcp resistances measured at aps/hep · 6/20/2013 · overview of the 8" mcp...

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