Subject: Re: stripixel stave resistance measurements
From: Eric Mannel <mannel@bnl.gov>
Date: 1/3/13 11:28 AM
To: "Sondheim, Walter E" <sondheim@lanl.gov>
CC: "Lynch, Don (dlynch@bnl.gov)" <dlynch@bnl.gov>, "PHENIX Vertex Vtx Detector (phenix-vtx-l@lists.bnl.gov)" <phenix-vtx-l@lists.bnl.gov>, "lenz@bnl.gov" <lenz@bnl.gov>

Walt-

To answer a few of your questions.  The measurements were taken using the stave that was removed this past fall and is in Chemistry.

The measurement between points A and E were made on bus side of the stave.  No attempt was made to scratch the surface of the stave.  My assumption, perhaps incorrect, is that there is a some type of non-conductive  coating on the carbon-fibre surface resulting in the high resistance reading.  Since the stave has sensors mounted on the other side completely covering the carbon-fibre surface, I was not able to measure the resistance between the 2 sides, although I expect it to be large if my assumption of a non-conducting coating is correct.

In the detector a grounding wire is attached with a non-magnetic metal screw to the aluminium block.  The other end of the ground wire is attached to the ground of the LDTB associated with the stave. The grounds of neighbouring LDTBs on a 1/2  big-wheel are connected with a short grounding wire.  The bottom LDTB on each 1/2 big-wheel is then connected to a local grounding block which  is connected to the PHENIX ground

Mike did confirm today that all grounds for the VTX Pixels, Strips and FVTX are properly connected.

Eric
 


On 01/03/2013 11:56 AM, Sondheim, Walter E wrote:

Hi Eric and Rachid thanks for making these measurements, I have attached two drawings, one is a layer 4 stave assembly and the other one is for a layer 4 stave core. I wanted to show you that the core is continuous from one side of the stave to the other. This laminated assembly is bonded together using non-conductive epoxy which is why the addition of grounding wires is critical to this assembly. The end blocks are made from different materials; the cooling tube exit end is made from Carbon loaded PEEK and the other end is 6061 Aluminum. Do you get similar measurement result on the stave that was removed last year, which I believe is still over in Chemistry? I am curious about your measurement A-E, which indicates that the two stave face sheets are not electrically connected. In the pictures you (Eric) posted earlier this week in slide #9 I see blue wires with ring lugs attached, how are these connected to the stave assembly? Do they connect to the Aluminum cooling tube?

Cheers, Walt

 

From: phenix-fvtx-l-bounces@lists.bnl.gov [mailto:phenix-fvtx-l-bounces@lists.bnl.gov] On Behalf Of Eric Mannel
Sent: Wednesday, January 02, 2013 10:17 PM
To: phenix-vtx-l@lists.bnl.gov; FVTX-List; Eric Anderssen; biggs@bnl.gov; Lynch, Don
Subject: stripixel stave resistance measurements

 

Dear All-

Rachid and I looked at resistances between different points on a barrel 4 stave this afternoon.  The attached slide show the nominal points we made measurements at.  All measurements were made using an inexpensive handheld DVM.

Point A: cooling tube end
Point B: cooling tube end
Point C: Side of stave (foam edge) near tube end
Point D: Side of  stave (foam edge) opposite end of stave from cooling tubes
Point E: Stave bus side
Point F: Stave End, bus side (Al end piece)  This is the point that is grounded to the LDTB and eventually PHENIX ground
Point G: Stave end, cooling side (peek end piece?)

Resistance between points as described above.
Resistance: A-B:  ~1 Ohm
Resistance: A-C:  ~8 Ohm
Resistance: A-D:  ~10 Ohm
Resistance: A-E: ~ 1 MOhm
Resistance: A-F: ~50 Ohms
Resistance: A-G: ~500 Ohms
Resistance: C-D: ~10 ohms

While I only recorded the resistance from the foam core to the cooling tube in 2 places on one side, I did check it several places on each side and the measurements were consistent with what I report above (8-10 Ohms).  There is a piece of foam core that lies in the "middle" of the U shaped cooling tube that I could not probe directly.  Point E is the surface side of the stave opposite the sensor (RCC side) which has an insulating epoxy covering.  Point F is the end that that grounding screw goes to and makes the reference connection to the LTDB, and subsequently to the PHENIX ground.

Eric

-- 
Eric J. Mannel, Ph.D.
Research Engineer
Dept of Physics/PHENIX
Brookhaven National Laboratory
914/659-3235 (cell) 

-- 
Eric J. Mannel, Ph.D.
Research Engineer
Dept of Physics/PHENIX
Brookhaven National Laboratory
914/659-3235 (cell) 


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