Optical Cluster Beam Studies & Production of Laval Nozzles Silke Grieser Westfälische Wilhelms-Universität Münster, Institut für Kernphysik PANDA Meeting Jülich, December 10th 2014 1 / 20
pumps cluster source dump beam chamber interaction pump additional Optical Cluster Beam Studies Cluster-jet Target MCT1S A compact cluster-jet target was built up at Münster Cluster source of the first target prototype for P ANDA Cluster-jet target will be used for laser induced ion accelertion in cooperation with ILPP (M. Büscher) Currently used for cluster beam studies (thickness, monitoring, position, stability...) �→ P ANDA 2 / 20
laser cluster beam laser beam laser beam dump cluster source Cluster beam analysis Interaction chamber Analysis of the cluster beam (position, relative thickness, stability, ...) 33 cm distance from the nozzle No possibility for movable rods (MCT2) CCD camera in combination with a dot laser Valuable for P ANDA 3 / 20
laser beam dump cluster beam cluster source laser CCD camera Cluster beam analysis Interaction chamber Analysis of the cluster beam (position, relative thickness, stability, ...) 33 cm distance from the nozzle No possibility for moveable rods (MCT2) CCD camera in combination with a dot laser Valuable for P ANDA 3 / 20
Cluster beam analysis Process of analysis Nozzle temperature: 22 K Gas pressure: 16 bar Exposure time: 15 s 4 / 20
Cluster beam analysis Process of analysis Nozzle temperature: 22 K Gas pressure: 16 bar Exposure time: 15 s 4 / 20
Cluster beam analysis Process of analysis Nozzle temperature: 22 K Gas pressure: 16 bar Exposure time: 15 s 4 / 20
Cluster beam analysis Projections 3 10 × -1 2000 / px x position 1500 dN 1000 500 0 200 400 600 800 1000 1200 x position / px 3 10 × -1 / px 2000 y position dN 1500 1000 500 0 200 400 600 800 1000 y position / px 5 / 20
Cluster beam analysis Projections 6 / 20
Cluster beam analysis Error Fit p ( x ) = I 0 · p e ( x − x 0 ) + I U x e − τ 2 d τ 2 � erf ( x ) = √ π 0 with p e ( x ) = x + d ∞ 2 1 1 − erf r − R � � � � dy dx 2 s x − d −∞ 2 I 0 : Height of the peak, intensity x 0 : Position of the maximum I U : Background R : Half peak width, radius s : Smearing factor � x 2 + y 2 r = 7 / 20
Cluster beam analysis Error Fit x + d ∞ 2 1 � � � 1 − erf r − R � p ( x ) = I 0 · p e ( x − x 0 ) + I U with p e ( x ) = dy dx 2 s x − d −∞ 2 × 3 10 -1 / px y position 2000 dN 1500 1000 500 0 200 400 600 800 1000 y position / px 8 / 20
temperatur / K pressure / bar gaseous liquid intensity / 10 5 arb. units 18 16 14 12 10 8 6 4 2 0 critical gaseous fluid supercritical fluid liquid 40 35 30 25 20 15 20 15 10 5 0 point supercritical Cluster beam analysis Result of the measurement: intensity Exposure time: 15 s 9 / 20
0 temperatur / K gaseous liquid thickness / 10 14 atoms/cm 2 8 7 6 5 4 3 2 1 critical pressure / bar fluid 40 35 30 25 20 15 20 15 10 5 0 point supercritical Cluster beam analysis Result of the measurement: thickness ρ T ∝ pressure increase 10 / 20
Production of new Laval nozzles Motivation Laval nozzle is the heart of a cluster source Specific convergent-divergent shape H 2 gas cluster Laval nozzle Production of a small inner diameter (< 30 µm) → a major technical challenge In the past these fine Laval nozzles were produced at CERN To ensure the production an improved production process based on the CERN production was recently developed at the University of Münster 11 / 20
Production process of the new Laval nozzles Negative of the trumpet 8,2 17,2 R60 7 � 4 Turned acrylic glass 46 30 to 60 µm at the narrowest point 12 / 20 � � � � � � � � � �
Production process of the new Laval nozzles Body of the Laval nozzle Galvanic deposition of copper Chloroform to remove remainder of the acrylic glass Accurate and clean extraction of the trumpet negative 13 / 20
Production process of the new Laval nozzles The final shape of the nozzle The final shape is turned out of the nozzle body 14 / 20
Production process of the new Laval nozzles Cone bore by fine mechanical workshop of institute Connection lasered by company Production of ring to fix the nozzle at the target cold head 15 / 20
The finished Laval nozzles An example of the first set Finished Laval nozzle of the first successfully produced set of 11 nozzles Inner diameter between 42 µm and 105 µm Initial measurements with these new nozzles at the PANDA cluster-jet target prototype (27 K, 5 bar) 16 / 20
The finished Laval nozzles An example of the first set Finished Laval nozzle of the first successfully produced set of 11 nozzles Inner diameter between 42 µm and 105 µm Initial measurements with these new nozzles at the PANDA cluster-jet target prototype (27 K, 5 bar) 16 / 20
Improvements Nozzle cut through by wire erosion 17 / 20
Improvements Drilling of the small inner diameter Above: drill (800-times magnified) Below: bore in aluminum (1500-times magnified) [Rabensteiner Präzisionswerkzeuge] 18 / 20
Improvements Drill by company „KERN“ → 3 nozzles with inner diameter of about 30 µm Drill does not reach the opening cone � Possible reasons: By the galvanic deposition the tip of the negative became skew got blunted 19 / 20
Summary & Outlook Cluster beam studies Development of optical method for cluster beam studies Possibility to do precise online cluster beam analysis about position, intensity, thickness, size, ... without any affecting of the beam during the operation of the experiment Production of Laval nozzles An improved production process was developed at the WWU Münster Initial measurements with new nozzles at the PANDA cluster-jet target prototype were performed Future investigations on the cluster production process to optimise the required target thickness More produced Laval nozzles and additional measurements at the PANDA cluster-jet target prototype will follow 20 / 20
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