Chemical and radiolytical characterization of some
perfluorocarbon fluids used as coolants for LHC
experiments
Part one: Chemical characterization
Part two: Radiation induced effects and purification
Sorin ILIEa, Radu SETNESCUa,b
aEuropean
Organization for Nuclear Research (CERN)
CH-1211 Geneva 23, Switzerland
bNational Institute in Electrical Engineering - Advanced Research (ICPE CA)
313 Spl. Unirii, Bucharest, Romania
SUMMARY
- Perfluorocarbon fluids were characterized by applying different methods:
GC, FT-IR, UV-Vis, potentiometry, distillation, etc.
- The first aim of this work was the quality control, the identification and the
quantification of different impurities which could increase the radiation
sensitivity of these fluids.
- The procedures settled-up in this work are sensitive to the presence of
disturbing impurities and were used for the analyses of the as received
perfluorocarbons and for the irradiated fluids.
- The second aim of this work was to assess the radiation induced
modifications on different fluids irradiated gamma Co 60:
acidity (HF), polymer & pre-polymers, new molecules, etc.
- Cleaning tests were carried out on the as received fluids and on the
irradiated ones to assess the efficiency of such purification treatments.
The main perfluorocarbon fluids studied in this work
Product name
Supplier
Composition
Name used
in this report
PF 5060
3M Chemicals, USA
mainly n-C6F14
(n-perfluorohexane)
PF 5060
2
PF 5060 "purified"
3M Chemicals, USA; tentatively
" treated" (purified) in CERN
Chemistry Laboratory
mainly n-C6F14
(n-perfluorohexane)
purified PF 5060
3
PF 5060 DL
3M Chemicals, USA
mainly n-C6F14
(n-perfluorohexane)
PF 5060 DL
4
Flutec PP1
F2 Chemicals Ltd., UK
mainly iso-C6F14
(iso-perfluorohexane)
PP1
5
C3F8
(R218)
ASTOR, Russia
C3F8
perfluoropropane
C3F8
perfluoropropane
No.
1
 Typical GC-TCD and GC-MSD spectra from the analyzed fluids are shown in Figs. 1 and 2.
 The purities of the received fluids were found to be higher as 98.5 %, conform to the CERN
Technical Specification.
 The chemical nature of some impurities present in n-C6F14 was found to be different from that
evidenced in iso-C6F14. The perfluorinated isomers and their homologous compounds, commonly
present, are not foreseen to be detrimental to the behavior of the cooling fluids during irradiation.
0
250000
4
8
12
16
2010000
560
150000
100000
1
50000
6000
2
520
500
4000
2000
3
2
1
3
0
540
0
480
10
20
Time (minutes)
30
Fig. 1 GC-MSD chromatograms for the studied
perfluorocarbons: (1) C3F8; (2) n-C6F14;
(3) iso-C6F14
0
10
20
30
40
Time (minutes)
50
0
60
Fig. 2 GC-TCD chromatograms for various
perfluorocarbons: (1) C3F8; (2) n-C6F14;
(3) iso-C6F14
Abundance
Abundance
Abundance
8000
200000
 In contrast, the presence of the H-containing molecules (such as hexane, hydrofluoroalkanes,
etc.) or of the double bonds containing ones (alkenes, hydrofluoroalkenes, perfluoroalkenes, etc.)
could result in an increased radiation sensitivity of the cooling fluids. (see Fig. 3 curve 1).
 The introduction of known and controlled impurities confirmed the assignment of the peaks (see
Fig. 4 a and b). The detection limit found for these impurities was around 30 ppm owing the used
analytical parameters.
 The results of the purification tests, illustrated in Figs. 3 and 4, confirmed a promising way to the
removal of the undesired impurities.
C6H14
60000
H-C6F13
Abundance
80000
40000
20000
1
2
0
10
20
30
Time (minutes)
Fig. 3 – GC-MSD chromatograms for the as received n-C6F14 (1) and the purified (2) one;
40000
C6CH6F14
14
1-HC6F13
r.t. = 30.08 min.
(b)
Abundance
Abundance
r.t. = 23.57 min.
(a)
1
1
30000
2
20000
3
2
3
23.4
23.5
23.6
23.7
Time (minutes)
23.8
10000
29.9
30
30.1
Time (minutes)
Fig. 4 Zoom on the GC-MSD chromatograms of n-C6F14 impurified with:
(a) hexane: 1 – 300 ppm; 2 – 30 ppm; 3 – purified;
(b) 1-HC6F13: 1 - 300 ppm; 2 - 30 ppm; 3 – purified.
30.2
30.3
(a)
6
5
4
0.005
3
2
1
0
3100
3000
2900
2800
-1
Absorbance (abs. units)
Wavenumber (cm )
(c)
0.01
3
0.005
3100
3000
0.2
y=Σan x
n
2900
2800
(b)
a0=0.000703151
a1=0.000239155
0.00183776
|r|=0.999563
0.1
0
2
1
0
Absorbance at 2968 cm -1 (abs. units)
Absorbance (absorbance units)
0.01
0
200
400
600
Hexane concentration (ppm)
800
-1
Wavenumber (cm )
Fig. 5
(a) FT-IR spectra in the region of 2900 cm-1 of n-C6F14 containing different amounts of hexane:
1 - reference (purified n-C6F14; 2 - 5 ppm; 3 - 10 ppm; 4 - 20 ppm; 5 - 50 ppm; 6 - C6F14 initial, as received
(b) The FT-IR calibration curve as a function of the hexane concentration and of the hexane like compounds
(c) Comparative spectra in the region of 3100 - 2800 cm-1 from controlled impurified C6F14 : 1 - reference
(pure C6F14); 2 - 1-HC6F13 300 ppm; 3 - hexane 50 ppm
(a)
7
Absorbance
6
0.04
5
0.02
4
0
1
1850
2 3
1800
1750
1700
Absorbance at 1786 cm -1 (abs. units)
0.06
Wavenumber (cm-1)
0.5
Σ
(b)
y= an xn
a0=0.000638613
a1=0.000124826
0.00105471
|r|=0.999976
0.4
0.3
0.2
0.1
0
0
1000
2000
1-C6F12 concentration (ppm)
Fig. 6
(a) FT-IR spectra in region of 1780 cm-1 from C6F14 samples impurified with C6F12:
1 - reference (pure C6F12); 2 - 20 ppm; 3 - 50 ppm; 4 - 100 ppm; 5 - 200 ppm;
6 - 386 ppm;
7 - 1000 ppm
(b) FT-IR calibration curve for determination of C6F12
3000
4000
UV-Vis results are also consistent to the GC data, the optical absorption in the spectral range 190 - 220 nm
being increased when perfluorohexene or 1-H perfluorohexane were added to pure C6F14.
All as received samples exhibited a certain optical absorption in UV spectral range, which was strongly
decreased following the purification treatment (Fig. 7 a, b).
1
7
6
2
Absorbance
(a)
UV absorbance at 195 nm
2.4
5
1.6
4
1.2
3
0.8
2
0.4
1
0 0
190
200
210
220
Wavelength (nm)
230
Σ
y= an xn
a0=0.0331278
a1=0.00734405
0.027509
|r|=0.995092
0.8
(b)
0.6
0.4
0.2
0
0
C6F12
50
100
concentration (ppm)
Fig. 7
(a) UV spectra in region of 190 – 240 nm from C6F14 samples impurified with C6F12:
1 - reference (pure C6F12); 2 - 20 ppm; 3 - 50 ppm; 4 – 100 ppm; 5 - 200 ppm;
6 - 400 ppm; 7 - 1000 ppm.
(b) The UV calibration curve at 195 nm for the C6F12 dosage.
Characterization of the initial fluids
Main results of the chemical characterization of the C6F14 fluids:  = test passed;  test not passed
Required value
Parameter
Fluid type
Units
Lower
limit
Upper
limit
PP1
PF 5060 as
received
DL
Purified PF
5060
C6F14 purity by GLC
(area %)*
%
98
-
99.259
98.964
99.023
99.052
Other PFC*
%
-
2
0.441
1.019
0.977
0.948
C6F14 double bonded
molecules
ppm
weight
-
10
< detection
limit 
detection
limit 
< detection
limit 
< detection
limit 
H containing
molecules
(equiv hexane)+
ppm
weight
-
10
< detection
limit 
722 
< detection
limit 
< detection
limit 
Free fluoride
(equiv. HF)
ppm
weight
-
1
0.05
0.06
0.03
0.02
Density
g/mL
1.660
1.700
1.721++
1.689 
1.694
1.689
°C
51
59
56
56
56
56x
Boiling point
*From GC-MSD measurements
+The content in H-substitutes PFC was below the detection limit in all cases as shown both FT-IR, GC-MSD and GC-TCD measurements
++The CERN imposed density value refers to n-C6F14; the value found in literature for pure perfluoro 2-methyl pentane (iso-C6F14) is
1.723 [http://www.chemexper.com/]; that given by the supplier (F2) is 1.725 g/cm3 [Certificate of Analysis Batch No 0294/ Ref. No.
P51917]. Thus, the measured density value corresponds to a pure fluid.
Characterization of the initial fluids
Main results of the chemical characterization of the C3F8 fluids:  = test passed;  test not passed
Parameter
C3F8 organic purity*
Other perfluorocarbons*
Unit
Lower limit
Upper limit
C3F8 (as analysed)
% volume
99.96
-
99.964 
ppm weight
-
400
360 (pefluorobutane)

10
not detected 
ppm weight
10
not detected 
ppm weight
0.1
0.08 
C3F8 double bounded
molecules*
ppm weight
H containing molecules*
Free fluoride
*GC-MSD
-
Conclusions on the chemical characterization of the perfluorocarbons
The aim of Part I of the work was successfully accomplished using the chemistry
laboratory analytical techniques and methods, which were sensitive to the parameters or
the properties of interest: these techniques should be used for the future characterization
and analyses.
 The following perfluorocarbon fluids supplied to CERN: PP1, PF 5060 DL, and C3F8
were found compliant to the CERN quality requirements and to the analysis certificates
delivered by the respective producers. PF 5060 as received and FC 72 were not
compliant in all points, as expected, to our quality requirements, mainly concerning the
hydrogen content.
 The acidity (HF content) of the all received fluids was below the imposed CERN limits.
The preliminary purification tests on less pure fluids were very promising. The work will
continue and the tests will be adapted and optimized, thus making other perfluorocarbon
fluids quality grades to meet the CERN quality requirements. In such a way the potential
suppliers and the range of the available fluids, possibly less expensive, may be
advantageously enlarged. A purified PF 5060 fluid was prepared in the laboratory and
used in irradiation tests.
IRRADIATED PERFLUOROCARBON FLUIDS
Expected doses: max. 30 kGy
Irradiation: two gamma 60Co doses: 28 kGy and 56 kGy
Irradiation configuration: 60Co source 150 kCi (IRASM)
Irradiated fluids
Radiation induced modifications:
- acidity (HF)
- polymers & pre-polymers
- new molecules
Cleaning (purification) tests of irradiated fluids
Conclusions
The types of irradiation containers
Irradiated perfluorocarbon samples
Bottle
no.
Content
PFC
weight
(g)
Dose
(kGy)
C1
C2
A01
A02
A03
A04
A05
A06
A07
A08
A09
A10
A11
A12
A13
A14
A15
A16
A17
A18
A19
A20
B01
B02
B03
B04
B05
PP1
PF 5060 (as received)
PF 5060 + air
PP1 + air
DL
Purified PF 5060
PF 5060 + hexane (1500 ppm)
PP1 + 1-C6F12 (1500 ppm)
PF 5060 + air (appl. 4 bar)
PF 5060 + air + H2O
PP1 + air (appl. 4 bar)
PP1 + air + H2O (0.5 mL)
PF 5060 as received (degassed 5' Ar)
PP1 (degassed 5' Ar)
DL
Purified PF 5060
PF 5060 + hexane (1500 ppm)
PP1 + 1-C6F12 (1500 ppm)
PF 5060 as received (degassed 5' Ar)
PF 5060 + air + H2O
PP1 (degassed 5' Ar)
PP1 + air + H2O
C3F8 (Astor) as recd.
C3F8 (Astor) + air
C3F8 (Astor) + air + H2O
C3F8 (Astor) + hexane 1500 ppm
C3F8 (Astor) + 1-C6F12 1500 ppm
ca. 5 000
ca. 5 000
908
611
924
902
896
868
900
905
609
904
892
803
899
918
878
998
900
895
903
907
423
418
514
516
505
28
28
28
28
28
28
28
28
28
28
28
28
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
* To be measured
Aluminum
m/S x 2105
No.
(g/cm )
43
*
39
*
40
*
41
+9.82 ?
33
+5.26
37
*
46
*
44
*
38
-2.46
30
*
32
*
45
-1.05
28
+1.05
31
*
27
+5.96
35
*
36
*
26
*
42
*
34
*
25
*
15
*
20
*
3
*
7
*
No.
42
40
31
41
36
44
39
38
27
33
45
32
28
34
30
35
37
43
29
26
52
50
48
49
51
Inox
m/S x 2105
(g/cm )
*
*
*
+ 1.75
+1.75
*
*
*
+0.70
*
0
+0.70
*
+1.75
*
*
*
*
*
*
*
*
*
*
Expected radiation induced chemical effects
General processes
Low molecular weight products
i.e. homologous PFCs (C1 - C5),
fluorinated molecules containing
double bonds, O, H (if oxygen, water
or other O or H sources are present),
e.g. alcohols, acids, carbonyl
compounds, alkenes etc.
C6F14
+
C6F13, F, C6F14*, C6F14 , e
-
Acidity increase
HF, F - and perfluoroacid formation
High molecular weight products
pre-polymers (soluble in C 6F14);nonvolatile residues) polymers (insoluble;
deposits over surfaces)
Similar proceses are expected for C3F8
Expected radiation induced chemical effects: F radical fate
recombination to form low molecular weight PFCs:
*
F3 C
F3C + CF2
cage
+F
CF4 + CF2
HF formation in presence of H sources:
F + H
HF +
recombination to result the initial molecule:
F +
C
C-F
 F atoms recombine with other radicals, resulting in a decrease of the final yield of
radiolysis;
CF4, C2F6, etc. formation is due to F reactions (F atoms have a great mobility; part of
them can escape to recombination)
 For thermodynamic reasons, F2 does not appears
 Higher molecular weight products may result as it is described below for C9F20
isomers resulting from the radiolysis of n-C6F14.
Expected radiation induced chemical effects: PFC's radicals fate
 Radiation induced radicals
CF3 + CF3(CF2)3CF2
C2F5 + CF3(CF2)2CF2
CF3CF2CF2 + CF3CF2CF2
F + CF3(CF2)4CF2
F + CF3(CF2)3CFCF3
F + CF3(CF2)2CFCF2CF3
n-C6F14
 Low molecular weight products
 High molecular weight PFCs (e.g.
C9F20) isomers
CF3 CF2 3CF2 + CF3 CF2 2CF2
CF3 + CF3
C 2 F6
CF3 + C2F5
C 3F8
CF3 + C3F7
C4F10
C 2 F5 + C 3 F7
C5F12
CF3 + C6F14
C2F5 + C6F14
CF4 + C6F13
C2F6 + C6F13
CF3CF2CF2 + CF3 CF2 4CF2
CF3CF2CF2 + CF3 CF2 3CFCF3
CF3 CF2 7CF3
(n-perfluoro nonane)
CF3 CF2 7CF3
(n-perfluoro nonane)
CF3 CF2 2CF CF2 3CF3
CF3
(perfluoro-4-methyl octane)
CF3CF2CF2 + CF3 CF2 2CFCF2CF3
CF3CF CF2 4CF3
CF2CF3
(perfluoro-2-ethyl heptane)
Expected radiation induced chemical effects
Water and oxygen complicate the reaction mechanism by their interference with the
perfluorocarbon radical reactions
Oxygen is a radical scavenger  leads to the formation of Carbonyl fluoride (CF2O)
or to other perfluorocarbonyl compounds
C6F13 + O2
2C6F13 OO
C6F13 OO
2 C6F13O + O2
C6F13O
C5F11 + CF2O
C6F13O
C4F9 + CF3CFO
Water is a relative simple substance.
However, it leads to many reactive species in a radiation field
Water radiolysis
Event
Time scale per s
H2O
+
H2O*
H2O + e
-
10
-16
H2O
+
H + OH
H2 + O
-14
OH + H3O
10
-13
10
-
eaq
formation of molecular products
in the spurs and diffusion of the
radicals out of the spurs
-
eaq, H, OH, H 2, H 2O2, H 3O +
10
-7
Possible reactions of the water radicals with perfluorocarbon or its radicals
C6F13 + H
C6F13 + OH
C6F14 + H
C6F13H
C6F13OH
C6F13 + HF
Expected radiation induced chemical effects - G values for products formation; in
red, there are the G values for radiochemical consumption of the parent
compounds (literature data)
Parent compound
Absorbed dose (kGy)
C3F8
n-C6F14
2-CF3C5F11
1430
1350
1450
Product
Molecules/ 100 eV
CF4
1.20
0.59
0.88
C2F6
0.85
0.29
0.28
C3F8
-3.74
0.31
0.21
n-C4F10
0.43
0.24
0.049
i-C4F10
0.40
-
0.18
n-C5F12
0.17
0.20
0.13
i-C5F12
0.27
0.019
0.085
n-C6F14
0.056
-2.88
0.050
2-CF3C5F11
0.13
-
-2.71
3-CF3C5F11
0.012
0.024
-
Total C7F16
0.0861
0.0108
0.3377
Total C8F18
-
0.16
0.19
Total C9F20
-
0.32
0.28
Total C10F22
-
0.21
0.12
Total C11F24
-
0.15
0.18
Total C11F24
-
0.042
0.069
Expected radiation induced chemical effects - G values for other molecules
resulted as radiolysis products (literature data)
Parent compound
Absorbed dose (kGy)
C3F8
n-C6F14
2-CF3C5F11
1430
1350
1450
Product
Molecules/ 100 eV
CO2
0.024
0.084
0.083
C2F6O
0.0057
-
-
C3F8O
-
-
-
(C2F5)2O
-
-
-
Unknown products (fluorinated
ethers and alcohols) (%)
0.0202
0.2920
0.0822
Radiation induced chemical effects - pH, HF and F- ions content
– laboratory measurements Fluid
Dose
(kGy)
Bottle
no.
Pressure
(mbar)
pH
HF
equivalent
(ppm)
F- (ppm)
PP1
Initial,
unirradiated
28 kGy
56 kGy
+ air (4 bar)
+ air + H2O
Initial,
unirradiated
28 kGy
56 kGy
Initial,
unirradiated
28 kGy
56 kGy
+ air (4 bar)
+ air + H2O
"
+ hexane
"
Initial,
unirradiated
28 kGy
56 kGy
0
-
-
5.90
0.042
0.05
28
56
28
28
C1
A12
A09
A10
- 130
+ 1925
- 50
PF 5060 DL
4.23
4.90
2.59
3.82
1.47
0.63
140
6.16
3.39
2.00
440
15
0
-
-
5.62
0.092
0.04
10.5
18
30
44
28
56
A03
-140
3.50
A13
-90
3.44
PF 5060 as received
0
-
-
5.43
0.098
0.06
28
56
28
28
56
28
56
C2
A11
A01
A08
A18
A05
A15
+ 180
+ 1375
+ 95
+ 215
+ 40
+ 100
Purified PF 5060
3.18
3.36
2.72
4.65
3.40
3.21
23
21
93
1.02
19
22
11.14
93
155
23
78
431
0
-
-
5.54
0.13
0.02
28
56
A04
A14
-155
-
3.55
3.48
17
19
47
55
Radiation induced chemical effects - pre-polymer content
– laboratory measurements Bottle no.
C1
C2
A01
A02
A03
A04
A05
A06
A07
A08
A09
A10
A11
A12
A13
A14
A15
A16
A17
A18
A19
A20
B01
B02
B03
B04
B05
PFC
Weight (g)
ca.
PP1
5 000
ca.
PF 5060 (as received)
5 000
PF 5060 + air
908 g
PP1 + air
611
DL
924
Purified PF 5060
902
PF 5060 + hexane (1500 ppm)
896
PP1 + 1-C6F12 (1500 ppm)
868
PF 5060 + air (appl. 4 bar)
900
PF 5060 + air + H2O
905
PP1 + air (appl. 4 bar)
609
PP1 + air + H2O (0.5 mL)
904
PF 5060 as received (degassed 5' Ar)
892
PP1 (degassed 5' Ar)
803
DL
899
Purified PF 5060
918
PF 5060 + hexane (1500 ppm)
878
PP1 + 1-C6F12 (1500 ppm)
998
PF 5060 as received (degassed 5' Ar)
900
PF 5060 + air + H2O
895
PP1 (degassed 5' Ar)
903
PP1 + air + H2O
907
C3F8 (Astor) as recd.
423
C3F8 (Astor) + air
418
C3F8 (Astor) + air + H2O
514
C3F8 (Astor) + hexane 1500 ppm
516
C3F8 (Astor) + 1-C6F12 1500 ppm
505
* To be measured
Content
Dose
(kGy)
28
pre-polymer
Content (%)
Total weight (g)
0.007
0.35
FT-IR
spectrum
565, 586,
588
557-560
28
0.147
7.35
28
28
28
28
28
28
28
28
28
28
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
0.067
*
0.021
0.031
0.074
*
*
0.103
0.0015
<6∙10-4
0.314
0.61
*
0.19
0.28
0.66
*
*
0.93
0.009
2.80
711
*
634
643
644
*
*
710
623, 630
<5.5∙10-4
0.016
0.097
*
*
*
0.14
0.89
*
*
*
685-688
642
*
*
*
0.0014
*
*
*
*
*
*
*
0.006
*
*
*
*
*
*
*
632
*
*
*
*
713
*
*
*
Radiation induced chemical effects - other molecules/GC-MS
(a)
(c)
(b)
Details of the chromatograms (GCMSD) of PP1 fluid initial and after
irradiation (gas phase analysis):
(a) focus on the initial portion, up to
the main peak of CF3C5F11 (not
shown);
(b) focus on the first peaks region;
(c) focus on the last part, after the
main peak (partly shown)
Radiation induced chemical effects - other molecules/GC-MS
(a)
Details of the chromatograms (GCMSD) of PP1 fluid initial and after
irradiation and purification
(liquid phase analysis):
(a) focus on the initial portion, up to
the main peak of CF3C5F11 (not
shown);
(b) focus on the last part, after the
main peak (partly shown)
(b)
Radiation induced chemical effects - other molecules/GC-MS
(b)
(a)
(c)
Comparison of the chromatograms
of PP1, DL, and PF 5060 fluids
irradiated at 56 kGy (gas phase
analysis):
(a) initial portion, up to the main
peak;
(b) zoom on the first portion to better
see the small peaks of PF 5060/ 56
kGy
(c) last portion, after the main peak
Radiation induced chemical effects - COF2 (FT-IR)
IR characteristic bands: 1944 cm-1 and 1925 cm-1
1925 cm-1
Absorbance (a.u.)
0.08
1944 cm-1
0.12
COF2 + H2O  CO2 + 2HF
1
0.04
2
0
2000
3
1900
1800
4
1700
Wavenumber (cm-1)
Evidencing of COF2 in liquid PP1: 1 - PP1 + air/28 kGy; 2 - PP1 + air/ 28 kGy after water
extraction; 3 - PP1/ 56 kGy-inert atmosphere; 4 - Reference unirradiated PP1
Radiation induced chemical effects – formation of COF2 (GC method)
Evidencing COF2 presence in
gaseous phase of the PP1 +
air/ 28 kGy by GC-TCD
analysis
Evidencing of COF2 in liquid
phase of the PP1 + air/ 28
kGy by GC-TCD analysis
Purification (cleaning) experiments on irradiated PP1 fluid (UV-VIS measurements)
2
0
4
1.6
5
6
-0.01
-0.02
-0.03
0.1
-0.04
200
220
240
260
Absorbance (a.u.)
Absorbance (a.u.)
0.2
3
1
Absorbance (a.u.)
Absorbance (a.u.)
0
1.2
2
0.8
3
-0.01
-0.02
-0.03
-0.04
Wavelength (nm)
1
4
200
0.4
220
240
260
Wavelength (nm)
0 1
0 1
200
220
240
260
280
200
300
260
280
1
2
-0.01
-0.02
1 - Ref. PP1 as received (référence);
2 – A19 PP1 56 kGy.
-0.03
-0.04
-0.05
200
220
240
300
1 - PP1 as received (reference); 2 – PP1 + air 28
kGy (A02); A02 + cartridge with 3 components
(2809): 3 – 75 min; 4 – 120 min.
1 - PP1 as received (reference); 2 - PP1 28 kGy
(C1); C1 + cartridge with 3 components (2809):
3 - 5 min; 4 - 30 min; 5 - 45 min; 6 - 75 min.
Absorbance (u.a.)
240
Wavelength (nm)
Wavelength (nm)
0
220
260
Wavelength (nm)
280
300
Purification (cleaning) experiments on irradiated PF 5060 fluid (UV-VIS measurements)
4
2
2
Absorbance (a.u)
Absorbance (u.a.)
3
2
3
4
1
3
3
2
5
1
7
5
0
0
1
200
220
240
260
280
300
Wavelength (nm)
1 - PF 5060 as received (reference); 2 - PF5060
28 kGy (C2); C2 + treatment by activated carbon
vegetal: 3 – 30 min; 4 – 60 min; 5 – 120 min.
4
6
1
200
250
300
350
Wavelength (nm)
1 - PF 5060 as received (reference); 2 – PF 5060
56 KGy (A11); A11 + treatment by cartridge with
3 components: 3 - 30 min; 4 – 60 min; 5 – 90 min;
A11 + 90 min cartouche 3 composants + SiO2:
6
– 30 min; 7 – 60 min.
Purification (cleaning) experiments on irradiated PF 5060 fluid (UV-VIS measurements)
(a)
(b)
GC-MSD spectra of the PF 5060 as received, irradiated (28 kGy) and cleaned after irradiation: the first part of
the chromatogram (a); the second part of the chromatogram (b).
The GC-MSD spectra of the as received and of the irradiated and subsequently purified PF 5060 are
quite similar.
Most of the supplementary peaks were identified as different perfluorocarbons.
The peaks of hexane or of other hydrogen containing compounds (e,g, C2F5H) traces existing in the
as received fluid were removed by the purifiers.
A very low content of 3-HC6F13 and other fluorocarbons containing oxygenated groups (ethers, carbonyl,
acid, etc.) was observed in the second part of the chromatograms and can be responsible of the residual
UV absorption after purification.
Purification experiments on irradiated as received PF 5060 fluid (FT-IR measurements)
0.8
0.08
Absorption (a.u.)
Absorption (a.u.)
0.12
3
0.04
2
0
0.6
3
0.4
2, 4
0.2
1
4
3400
1
0
-0.04
3200
3000
2800
-1
Wavelength (cm )
2000
1900
1800
1700
1600
1500
-1
Wavelength (cm )
FT-IR spectra of as received PF 5060 fluid in the spectral range 3400 - 2800 cm-1 (a)
and 2000 - 1500 cm-1 (b):
1-reference air; 2 - as received; 3 - irradiated at 28 kGy; 4 - cleaned after irradiation
- All FT-IR spectra of the initial, irradiated and cleaned PF 5060 fluid were similar, excepting the regions
of 3400 - 2800 cm-1 (a) and 2000 - 1500 cm-1(b).
-The cleaning treatment eliminates almost completely the H - containing molecules (3400 - 2800 cm-1).
-Other O – containing molecules (carbonyl, carboxyl, ether...), structurally similar to the main component,
are responsible for the small absorption increase at 2000 - 1500 cm-1 and were removed also in the
purification process.
- It can be concluded, based on GC-MSD and FT-IR data, that the cleaning treatments are efficient even
for the irradiated PF 5060 fluid; the observed UV absorption is probably due to traces of molecules with
very high optical absorption coefficients.
CONCLUSIONS
•
the Part I of the work was successfully accomplished; for the Part II a part of the work is still
ongoing;
•
the chemistry laboratory analytical techniques and methods were sensitive to the parameters of
interest and will be used for the future analyses of perfluorocarbon fluids;
•
the following perfluorocarbon fluids supplied to CERN: PP1, PF 5060 DL and C3F8 were found
compliant to the CERN quality requirements, while FC-72 and PF 5060 were not;
•
the purification tests on less pure fluids were very promising; the potential suppliers and the
acceptable quality of the fluids may be advantageously enlarged;
•
various perfluorocarbon fluids, as received and/or modified in laboratory were irradiated using
gamma 60Co at 28 kGy and 56 kGy doses;
•
radiation induced acidity, the presence of polymers or pre-polymers, the appearance of new
chemical species, etc. were evidenced and measured;
•
it was evidenced the higher radiation hardness of PP1 fluid (i-C6F14) as compared to PF 5060 DL
(n-C6F14)
•
the cleaning tests of irradiated fluids have shown a very good efficiency for the as received PP1
fluid (i-C6F14) and an acceptable efficiency for the n-C6F14.