1. 33mm MCP Testing at UC Berkeley
Jason McPhate
Experimental Astrophysics Group
Space Sciences Laboratory
University of California, Berkeley
15 Oct 2009
J. McPhate – PSEC Collaboration Meeting

2. MCP Testing Methodologies
Phosphor screen imaging
Single MCP imaging (uniformity of gain × QE, multi-fiber modulation)
No simple gain measurement  Cannot separate gain and QE effects
Photon counting imaging
Requires more stack gain than single MCP
Separates gain and QE effects
Measure pulse height distribution (PHD)
PHD characterization verses stacking scenarios
15 Oct 2009
J. McPhate – PSEC Collaboration Meeting

3. Phosphor Screen Image Testing
Interior Views
Exposed
Phosphor
Screen
Input
Solid
Edged
MCP
Loaded
Output
Glass
Fiber
Exterior View
Phosphor screen readouts
Imaging of single MCPs
Characterize gain×QE variations
Characterization of multi-fiber modulation
Not photon counting  cannot separate gain and QE
15 Oct 2009
J. McPhate – PSEC Collaboration Meeting

4. Example of Phosphor Screen Imaging (More Later)
Older 6µm pore MCP
– multi-fiber modulation evident
Newer 6µm pore MCP
– multi-fiber pattern completely gone.
15 Oct 2009
J. McPhate – PSEC Collaboration Meeting

5. Flexible 33mm MCP Photon Counting Demountable Detector Design
Top Clamp Plate
Compression Spacers
Compression Spring
Φ33mm MCPs
RT/Duroid Spacer
PEEK Body
Base Plate
Pressure Pad
Some piece parts have arrived (above) for 6 assemblies. We brought 2 assemblies to ANL.
Awaiting other parts fabrication:
RT/Duroid MCP spacers
Pressure pads and springs
Compression spacers
15 Oct 2009
J. McPhate – PSEC Collaboration Meeting

6. Example of a Similar Demountable
When complete the 33mm MCP demountable will be similar to this.
Mounted on CF flange above a cross- delay anode readout.
CF flange has feedthroughs for HV and anode signals.
PEEK sandwiches base plate for rear field stand-off and hold down.
Two more HV’s for MCP gap voltages (four total).
This style detector is very useful for rapid MCP restacking and optimizing.
15 Oct 2009
J. McPhate – PSEC Collaboration Meeting

7. Example of Photon Counting Imaging
Photonis MCP “Z” stack (8µm top, 10µm mid/bot). Cross delay line readout.
Counts image. Slight multi-fiber modulation visible, “dead” spots clear
Gain map image (average gain per pixel). Multi-fiber modulation more evident
15 Oct 2009
J. McPhate – PSEC Collaboration Meeting

8. Some Standard MCP Metrics
MCP Stack Gain vs. Voltage
Photon vs. Background PHDs
Photon PHD vs. Voltage
Stack PHD Width vs. Gain
15 Oct 2009
J. McPhate – PSEC Collaboration Meeting

9. Double Barrel 33mm MCP Test Station
We are in the final stage of refurbishing a dedicated dual chamber vacuum station for 33mm MCP testing
Separate chambers for phosphor screen detector and photon counting detector.
Each chamber has independent roughing and hivac valves  uninterrupted testing of one detector while the other is swapped.
8” CF flanges for detector mounting  lots of room for feedthroughs.
Will be using Viton gasket here for quick change out.
Turbo pump system with a dry scroll pump for a clean reliable system.
UV transmissive windows to illuminate detectors
15 Oct 2009
J. McPhate – PSEC Collaboration Meeting

10. ALD Coatings on 33mm Glass MCPs
Two standard glass Photonis MCPs (R ~ 90MΩ) sent for Al2O3 ALD coating over approximately half the active area. 6nm and 12nm coatings.
Resistances unchanged by coatings.
Jig for ALD coatings on 33mm glass MCPs. Stainless plates and PTFE gaskets with matching half moon cutouts.
ML201-B-1 – 6nm ALD on glass MCP, post-ALD, post-cleaning (similar both sides)
ML201-B-2 – 12nm ALD on glass MCP, post-ALD, post-cleaning (similar both sides)
15 Oct 2009
J. McPhate – PSEC Collaboration Meeting

11. 6nm Al2O3 ALD on Standard MCP Phosphor Screen Imaging
Definite enhancement of brightness in ALD area.
No degradation of image quality (except in boundary region).
ML201-B-1: 86MΩ, UV flood illumination, 1050V MCP, 2900V screen.
ML201-B-1: 86MΩ, UV flood illumination, 1150V MCP, 2800V screen.
15 Oct 2009
J. McPhate – PSEC Collaboration Meeting

12. 12nm Al2O3 ALD on Standard MCP Phosphor Screen Imaging
Dramatic decrease of brightness in ALD area.
Theory for 6nm/12nm Difference
Brightness is product of QE × gain.
Matt Wetstein’s testing indicates Al2O3 ALD increases gain (better SEE).
NiCr electrode acts a photocathode on bare MCP.
ALD covers the NiCr and has poorer UV response.
All is explained if the 6nm ALD permits photoelectrons from the NiCr through, but the 12nm coating does not.
In light of this, where the electrode layer is placed (above/below the SEE layer) has ramifications on tube processing.
ML201-B-2: ~90MΩ, UV flood illumination, 1150V MCP, 2700V screen.
15 Oct 2009
J. McPhate – PSEC Collaboration Meeting