THz and sub-THz waves for
water status detection
CROP.SENSE.net S4 & S5,
and further developments
shortened version – previously unpublished material removed
R. Gente, N. Born, A. Rehn, M. Koch
CROP.SENSe.net Symposium, Bonn, 29.9.1014
Outline
•  Introduction to THz technology
•  Summary of CROP.SENSE.net S4 & S5:
–  System development
–  Measurements
•  Further developments (after CROP.SENSE.net ended for us):
–  Sub-THz scattering measurements
–  Automated long-term THz measurements
•  Outlook
Introduction to THz technology
visible
10
7
10
THz
micro waves
radio waves
8
10
9
10
10
10
11
10
infrared
12
10
13
10
ultraviolet
14
10
15
frequency (Hz)
•  THz radiation: 0.1 – 10 THz
•  High contrast between water and most other materials
10
16
X-ray
10
17
CROP.SENSE.net S4: system development
!
See also: R. Gente et al., Journal of Infrared,
Millimeter, and Terahertz Waves, 34(3-4), p.316, 2013
19” rack case:
•  laser
•  delay-unit
•  electronics
Handheld
measurement head:
•  THz emitter and
detector
•  THz optics
Customized software for
data analysis
CROP.SENSE.net S4: measurements on barley
•  Measurements performed in Bonn (GS2, Prof. Léon)
•  63 pots for 14 days
–  3 groups: control, drought stress and completely dry
90
control
drought stress
completely dry
85
THz
water content (weigth−%)
gravimetric
80
75
70
65
60
55
50
1
2
3
4
5
6
7
8
9
10
11
12
13
day
•  THz measurements and invasive technique agree well
•  Non-destructive determination of water content is possible
CROP.SENSE.net S5: system development
60 GHz
emitter
light source
35 GHz
emitter
35 GHz
detector
camera
60 GHz
detector
measurement
spot
•  Plant is placed in the intersection of the different beam paths
•  Rotation of the plant allows averaging
CROP.SENSE.net S5: measurements on barley
•  Measurements performed in Bonn (GS2, Prof. Léon)
•  63 pots for 14 days
–  3 groups: control, drought stress and completely dry
90
control
drought stress
completely dry
water content (weigth−%)
85
Sub-THz
gravimetric
80
75
70
65
60
55
1
2
3
4
5
6
7
day
8
9
10
11
12
13
•  Sub-THz measurements and invasive technique agree well
•  Non-destructive determination of water content is possible
Outlook
•  More long-term measurements on agricultural crops
•  Adapt THz quasi time domain technology for water status
measurements:
–  Cheaper laser
–  More compact setup possible
Thanks & Acknowledgements
•  W. Sannemann, M. Noschinski, A. Ballvora, J. Léon
•  D. Behringer, S. Liepelt, U. Mattern, S. Beyer, B. Ziegenhagen
•  M. Schwerdtfeger, M. Stecher, M. Reuter, S. Busch
This work was supported by the German Federal Ministry of
Education and Research (BMBF, FKZ 0315532D)
and the Johannes Hübner Foundation Gießen.
Thank you for your attention!