1. MCP Electrodes and End Spoiling
Jeffrey Elam, Qing Peng, Anil Mane, Thomas Prolier, Joe Libera
Argonne National Laboratory
Large Area Photodetector Collaboration Meeting
October 15, 2009

2. MCP Structure resistive coating (ALD) emissive coating (ALD)
pore
resistive coating (ALD)
emissive coating (ALD)
conductive coating (thermal evaporation or sputtering)

3. RF Magnetron Sputtering System, AJA International ATC 2400
John Pearson, MSD
Sputtering system
Sample rotation
Deposition chamber
Load lock
Sample transfer Arm

4. We’re done, right? No. RF Magnetron Sputtering on Au/Cr Electrodes
Uncoated MCP
MCP
100nm AZO
MCP+100nm AZO+Cr 5nm+Au 50nm
We’re done, right?
No.

5. Electrodes and End-Spoiling in MCPsb
Endspoiling: h=b/d

6. End spoiling output side: increases spatial resolution decreases gain
Importance of End Spoiling
IEEE Trans Nucl. Sci. 19 (3)  1972
End spoiling output side:
increases spatial resolution
decreases gain
trade-off: h~1-2
Input side: h~

7. N(E) becomes more narrow as end spoiling increases
Effect of End Spoiling on Electron Energy Distribution A B
(end spoiling)
N(E) becomes more narrow as end spoiling increases

8. N(E) narrows as end spoiling increases
Effect of End Spoiling on Electron Energy Distribution
Simulations:
h=0
h=0.5
h=1
h=3
N(E) narrows as end spoiling increases

9. small increase in spatial resolution (10%) with 1.5 end-spoiling
Effect of End Spoiling on MCP Spatial Resolution
small increase in spatial resolution (10%) with 1.5 end-spoiling

10. Effect of End Spoiling on MCP Spatial Resolution
Simulations:
h=0
h=0.5
h=1
h=3
No systematic change in angle distribution with end-spoiling

11. Gain ~ (SEC) (L/z) exp(-0.65h)
Effect of End-Spoiling on MCP Gain
Gain ~ (SEC) (L/z)
SEC=secondary electron coefficient
L=pore length
z=distance between collisions
Since E field gradient=0 in electrode length h, no gain there
Gain ~ (SEC) (L/z) exp(-0.65h)
Gain decreases with end-spoiling

12. Gain decreases with end-spoiling
Effect of End-Spoiling on MCP Gain
100
h=1.2
h=2.2
h=3
h=4
IEEE Trans Nucl. Sci. 19 (3)  1972 10
Gain 1
0.1
0.01
Voltage
Gain decreases with end-spoiling

13. Sputtering is not “line-of-site” Need to use evaporation
Controlling End-Spoiling
RF-magnetron sputtered
Ti and Cu in high aspect ratio trench
Sputtering is not “line-of-site”
Need to use evaporation
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14. Controlling End-Spoiling
h=atan(θ)

15. Price to coat 8” square ($)
Electrode Materials
Ossy suggests: 200 nm Inconel 600, h=1-2.
metal
melting Point °C
Resistivity
µΩ cm
thermal conductivity
W/mK
Vickers
Hardness
MPa
Adhesion
Oxidation Resistance
Price to coat 8” square ($)
Inconel 600
1400
104 15
638
Great OK
$0.3
Gold
1064
2.2
318
216
Terrible
Best $6
Copper
1084
1.7
401
369
Poor
$0.06
Inconel 600: Trademark of Special Metals Corporation
Nichrome:
Brand name, range of compositions
Ni %
Cr ~17%
Fe ~10%
Mn ~1%
Ni ~80%
Cr ~20%

16. Thermal Evaporation System, BOC Edwards AUTO 306
Hau Wang, MSD

17. ~200nm thermal evaporated NiCr on 33 mm ALD MCP
Thermal Evaporation System, BOC Edwards AUTO 306
Hau Wang, MSD
sample rotation motor
~200nm thermal evaporated
NiCr on 33 mm ALD MCP
(end-spoiling not controlled)