I started with a ship full of max-level veterans, and I'm just a complete noob.

The following morning, the acceptance inspection before the fourth furnace was carried out on time.

Old Sun placed the finished and finely ground quartz crucible onto the inspection table.

The light shone through the transparent sidewall, clearly revealing the transition between the bottom rounded corner and the sidewall that was marked last night.

Fang Xudong used a micrometer to re-measure each point along the circumference, and the maximum difference in wall thickness was controlled within 0.1 millimeters. The bottom center and edge also fell within the tolerance range of the drawing.

Jiang Ming checked the inspection records left from last night and signed his name in the acceptance column of the processing drawing.

Old Sun wiped the quartz powder off the outside of the crucible, placed it on the balance, and then took the graphite crucible used in the previous batch for comparison.

After copying the two readings onto the back of the processing diagram, Jiang Ming added the material thermal conductivity differences and estimated heat capacity next to them.

"Quartz is lighter and conducts heat more slowly, so it stores less heat inside the walls, and the furnace's temperature response will be faster than the previous furnace." He moved the machining diagram to the control panel, "The original knob positions need to be recalibrated."

The mass, specific heat, and contact area of ​​the two crucibles were then substituted into the simplified thermal model, and the time constant between the heating seat and the melt was quickly calculated.

The response time of the quartz crucible is significantly shortened. The original proportional gain can continue to be used, and the controller is prone to repeated corrections near the set temperature, and the integral accumulation will also be faster.

He removed the lead seal on the control panel, recalibrated the positions of the proportional and integral knobs, slowed down the proportional effect, and lengthened the integral time accordingly. Then he had Da Liu connect the simulated load to conduct a step test.

The original spring used in the actuator returned too slowly, so Da Liu took out a spring with more suitable elasticity from the spare parts rack, installed it, and retested the opening change.

The recording pen drew two response curves on the paper tape. The second overshoot was already within the allowable range, and there was no continuous oscillation during the fallback process.

"After the official heating begins, we need to observe the melt load; the no-load parameters are only a starting point."

Jiang Ming sealed the knobs that were not in use temporarily, recorded the new calibration position in the fourth furnace process card, and then asked Lao Sun to install the quartz crucible.

The same batch of germanium material, after six rounds of regional purification, was loaded into the crucible according to the weight of the previous furnace. The seed crystal, protective gas flow rate, and furnace pressure were also kept at the original conditions to prevent new variables from being mixed into the control results.

After the heating began, the edges of the germanium block gradually softened, and the silvery-gray liquid surface spread out from the bottom, directly revealing the changes inside the melt through the quartz sidewalls.

When using a graphite crucible in the previous furnace, observation could only rely on the top window, making it difficult to see the liquid flow and suspended matter near the crucible wall. This time, Fang Xudong could take continuous photos of the melt through the side window.

He fixed the camera on a tripod and took a picture at the same time intervals. The color of the melt was evenly distributed in the picture, and no dark particle bands caused by fine graphite particles could be seen near the crucible wall.

After the temperature entered the stable zone, Jiang Ming observed the rate of drop on the paper tape and then adjusted the integration knob one notch to the slow end, so that the controller could adapt to the faster thermal response of the quartz crucible.

Old Sun lowered the seed crystal to the liquid surface and first used a handwheel to make contact. The liquid germanium spread along the bottom surface of the seed crystal, forming a smooth crescent.

Jiang Ming confirmed that the solid-liquid interface edge remained stable, and instructed Da Liu to gradually increase the rotation speed of the rotating mechanism to 28 revolutions per minute. Fang Xudong simultaneously recorded the motor current, worm gear cycle, and temperature ripples.

Once the rotation speed is reached, the lifting mechanism begins to rise at a rate of 0.8 millimeters per minute, and a continuous metallic gray crystal column gradually grows below the seed crystal.

The melt flow behind the quartz sidewall is easier to observe. A stable axial flow is formed near the bottom of the seed crystal, and no polygonal ridges appear on the edge of the liquid surface.

When the lifting process reaches the middle stage, the furnace temperature shifts downward due to the actuator's first return. The controller then replenishes the output, and the meniscus narrows only slightly before stabilizing again.

Jiang Ming marked the corresponding positions on the process card and continued to observe the growth lines on the side of the crystal without adjusting the rotation and pulling parameters.

Forty-five minutes later, the melt height was close to the stop line. Lao Sun stopped the rising mechanism and kept it rotating, allowing the crystal to detach smoothly from the liquid surface.

The fourth batch of single crystals, after cooling, was about 36 millimeters long, with a continuous metallic luster on the surface, and the tail end was neater than that under the graphite crucible conditions.

Fang Xudong first cut off the thin slice at the tail end, and after polishing, sent it to a polarizing microscope. The changes in brightness and darkness in several directions remained consistent, and the entire crystal maintained the same orientation.

The four-probe measuring station was then set up. Lin Lanying moved the probes at fixed intervals, Fang Xudong controlled the current and reported the readings, and Jiang Ming converted each measuring point into resistivity.

The data at the beginning was slightly higher, the changes narrowed after the middle section entered the flat zone, and there was still a decline at the end, but the decline was narrower than that of the third furnace.

After recording the last measurement point, Fang Xudong connected the curve to the coordinate paper and recalculated the difference between the beginning and end of the curve.

"Eleven percent."

Wu Hanzhang put the preliminary research plan in his hand on the table, walked to the coordinate paper to check the first and last values, and then asked Fang Xudong to recalculate it according to the effective length.

The second calculation still fell to around 11%, a decrease of 5 percentage points from the 16% of the third furnace of the graphite crucible, and also close to the target range previously given by Jiang Ming.

Jiang Ming substituted the measured curves back into the effective segregation coefficient model to deduce the interfacial impurity transport under the conditions of the fourth furnace, and then compared it with the crucible usage records of the third furnace.

The additional impurities contributed by the graphite crucible wall decreased by about 70% after replacing the quartz crucible. The remaining deviation mainly came from the residual impurities in the germanium material itself, as well as the enrichment at the tail end caused by the limited crystal length.

Fang Xudong took out the coordinate paper from the first few batches and stacked the resistivity curves of the second, third, and fourth batches on the same sheet of transparent paper.

The differences between the beginning and end of the three curves are 30%, 16%, and 11%, respectively. The changes in the boundary layer and the crucible material caused by the increase in rotational speed each leave a clear improvement margin on the curves.

He wrote down next to the second curve that the rotation speed increased from twelve revolutions to twenty-eight revolutions, and next to the third curve he marked that the quartz crucible and carbon impurities decreased.

After looking at the stacked diagrams, Wu Hanzhang patted the edge of the table with his palm.

"Eleven percent, is that enough for cutting components?"

Jiang Ming placed the fourth batch of single crystals on the measuring rack, avoiding the transition zone at the beginning and end, and cut out a one-centimeter length from the middle section. Then he asked Fang Xudong to repeat the measurement at a closer spacing.

The internal resistivity change in this section is controlled within ±3%, the crystal orientation is continuous, and no obvious defects are visible on the surface, which already meets the requirements for the trial production of the first-generation point contact germanium diode.

"We can start the trial production. Cut the first batch from the middle section, keep the head section for later comparison, and continue to seal the tail section."

Wu Hanzhang picked up the preliminary research plan, wrote "the middle section of the fourth furnace" after the mixer diode material column, and moved up the start date of the device group to the next week.

"Old Sun makes the cutting fixture, Da Liu checks the contact spring pressure, and Fang Xudong inputs the material number and resistivity into the device process card."

After making the arrangements, Jiang Ming returned to his cubicle and condensed the process record for the fourth furnace into a technical bulletin, addressed to Wang Shouwu.

The report lists the quartz crucible mass, heat capacity changes, PID retuning parameters, fourth furnace crystal pulling conditions, and resistivity distribution, and includes a comparison of theoretical predictions with 11 percent of the actual measurements.

At the end of the letter, he added a line of technical advice.

"If seed crystals with a purity of 99.9% or higher can be obtained in the future, the uniform section at the head can be further extended."

Upon seeing this sentence, Fang Xudong raised his hand and pointed to Wang Shouwu's name.

"His lab has been working on seed crystal preparation. Send this report over, and he should understand what you mean."

Whether or not to give it to him after he understands it is his choice.

Jiang Ming put the report into an internal document exchange bag, stamped it with the seal of the 502 Technical Group, and handed it to Comrade Song to be sent to the Institute of Physics.

Two days later, the file bag was returned to 502. On the cover, there was an additional reply written by Wang Shouwu: "I will be at the factory this afternoon. I brought the seed crystal with me."

After Jiang Ming finished reading, he placed the fourth furnace process card and the seed crystal clamp diagram on Fang Xudong's recording table, asking him to make room for inspection in advance.