this afternoon, I started the heating cable after the warm-up of the FP-cavity :
14h20 : start to fill 50kW in the cavity
15h : start of the heating cable @10V (2x 5V) (iteration 2300)
15h16 : start of the heating cable @60V (2x 30V) (iteration 3400)
15h20 : start of the heating cable @20V (2x 10V) (iteration 3600)
the offset frequency, for 20V of voltage on the DC voltage supply, is 175Hz @500MHz (equivalent to 3.5µm)
| Ronic Chiche wrote: |
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today, I removed one of the DC voltage supply (as with 30V, we are already able to 30°C on the heating cable).
the remaining DC voltage supply is configured in series (2x30V = 60V max) and is at the IP address : 192.168.1.101
| Ronic Chiche wrote: |
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several days ago, we installed a heating cable around the output flange (close to the X-hutch) of the FP-cavity vessel.
we are able to heat this cable by applying a DC voltage coming from 2 DC voltage supplies in serie (2 devices with 2x 0-30V / 3A => 0-120V / 3A).
currently, we apply at maximum 7V DC on each channel => 28V DC on the cable. its temperature reach ~ 30°C after 1/2h or more.
this temperature increase on one vessel of the FP-cavity, changes very slowly the length of the FP-cavity.
see this post (red curve on fig. 2) for a typical temperature curve measured (exponential-like curve) on the heating cable itself : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/290
the length change rate of the FP-cavity, due to this heating, is difficult to estimate because it depends on the part of this exponential curve you make the measurement.
but globally the drift is about 50nm every 5 minutes, which is roughly equivalent to 10 steps of the FP-cavity motor every 5 minutes.
| Ronic Chiche wrote: |
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as the CFP motors displacements induce a cavity unlock, we try to change the cavity length by changing the temperature of elment of the cavity.
yesterday, we tried to put a "heating cable" borrowed to the vacuum group to change the temperature of one bellows between the FP-cavity and the electron ring.
we chose a below because it is flexible and should not apply a too strong force on the cavity vessels.
we heated the cable at ~30°C but we didn't see a clear effect on the FP-cavity frequency measurement.
then, we put a heating cable around the X-ray output flange of the FP-cavity vessel and we saw a clear effect : a relatively fast (at a "second" level) frequency change.
the problem is the heating system is not remotely driven.
the cable is R=55ohms impedance and can reach 450°C for 1kW dissipated.
so today, we will try to use 2 remotely controlled Siglent SPD3303X power supplies.
they can reach V=120V DC => P=V²/R=260W => we could reach more than 100°C
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